Use __slots__ for small classes

tensorflow/python/data/ops/dataset_ops.py

@@ -3770,6 +3770,8 @@ class BatchDataset(UnaryDataset):
 class _NumpyIterator(object):
   """Iterator over a dataset with elements converted to numpy."""
 
+  __slots__ = ["_iterator"]
+
   def __init__(self, dataset):
     self._iterator = iter(dataset)
 

tensorflow/python/data/ops/iterator_ops.py

@@ -522,6 +522,8 @@ class IteratorResourceDeleter(object):
   object is part of a reference cycle, the cycle will be collectable.
   """
 
+  __slots__ = ["_deleter", "_handle", "_device", "_eager_mode"]
+
   def __init__(self, handle, device, deleter):
     self._deleter = deleter
     self._handle = handle

tensorflow/python/data/ops/multi_device_iterator_ops.py

@@ -377,6 +377,9 @@ class MultiDeviceIteratorResourceDeleter(object):
   object is part of a reference cycle, the cycle will be collectible.
   """
 
+  __slots__ = ["_deleter", "_multi_device_iterator", "_iterators",
+               "_device", "_eager_mode"]
+
   def __init__(self, multi_device_iterator, iterators, device, deleter):
     self._deleter = deleter
     self._multi_device_iterator = multi_device_iterator

tensorflow/python/distribute/device_util.py

@@ -84,6 +84,8 @@ def resolve(d):
 class _FakeNodeDef(object):
   """A fake NodeDef for _FakeOperation."""
 
+  __slots__ = ["op", "name"]
+
   def __init__(self):
     self.op = ""
     self.name = ""

tensorflow/python/distribute/distribute_lib.py

@@ -250,6 +250,8 @@ def get_update_replica_id():
 class UpdateContext(object):
   """Context manager when you are in `update()` or `update_non_slot()`."""
 
+  __slots__ = ["_replica_id", "_old_replica_id"]
+
   def __init__(self, replica_id):
     self._replica_id = replica_id
     self._old_replica_id = None
@@ -454,6 +456,9 @@ class InputContext(object):
   source etc).
   """
 
+  __slots__ = ["_num_input_pipelines", "_input_pipeline_id",
+               "_num_replicas_in_sync"]
+
   def __init__(self,
                num_input_pipelines=1,
                input_pipeline_id=0,
@@ -545,6 +550,8 @@ class ValueContext(object):
 
   """
 
+  __slots__ = ["_replica_id_in_sync_group", "_num_replicas_in_sync"]
+
   def __init__(self,
                replica_id_in_sync_group=0,
                num_replicas_in_sync=1):
@@ -2923,6 +2930,8 @@ class _DefaultDistributionStrategy(StrategyV1):
 class _DefaultDistributionContext(object):
   """Context manager setting the default `tf.distribute.Strategy`."""
 
+  __slots__ = ["_var_creator_scope", "_strategy", "_nested_count"]
+
   def __init__(self, strategy):
 
     def creator(next_creator, **kwargs):

tensorflow/python/eager/cancellation.py

@@ -24,6 +24,8 @@ from tensorflow.python import pywrap_tfe
 class CancellationManager(object):
   """A mechanism for cancelling blocking computation."""
 
+  __slots__ = ["_impl"]
+
   def __init__(self):
     self._impl = pywrap_tfe.TFE_NewCancellationManager()
 

tensorflow/python/eager/context.py

@@ -80,6 +80,8 @@ _python_eager_context_create_counter = monitoring.Counter(
 class _EagerTensorCache(object):
   """Simple cache which evicts items based on length in a FIFO manner."""
 
+  __slots__ = ["_data", "_max_items", "_max_tensor_size"]
+
   def __init__(self, max_items=256, max_tensor_size=10000):
     self._data = collections.OrderedDict()
     self._max_items = max_items
@@ -107,6 +109,8 @@ class FunctionCallOptions(object):
   Eager functions are functions decorated with tf.contrib.eager.defun.
   """
 
+  __slots__ = ["_config_proto_serialized", "_executor_type"]
+
   def __init__(self, executor_type=None, config_proto=None):
     """Constructor.
 
@@ -161,6 +165,8 @@ _tensor_caches_map = {}
 class _TensorCaches(threading.local):
   """Thread local tensor caches."""
 
+  __slots__ = ["_ones_rank_cache", "_zeros_cache"]
+
   def __init__(self):
     super(_TensorCaches, self).__init__()
     self._ones_rank_cache = None
@@ -316,6 +322,8 @@ class PhysicalDevice(
 class _AtomicCounter(object):
   """A simple atomic counter."""
 
+  __slots__ = ["_value", "_lock"]
+
   def __init__(self):
     self._value = 0
     self._lock = threading.Lock()
@@ -332,6 +340,8 @@ _context_id_counter = _AtomicCounter()
 class _TensorCacheDeleter(object):
   """Deletes tensor caches for a given context."""
 
+  __slots__ = ["_context_id"]
+
   def __init__(self, context_id):
     self._context_id = context_id
 
@@ -1730,6 +1740,8 @@ class Context(object):
 class _EagerDeviceContext(object):
   """Context-manager forcing placement of ops and Tensors on a device."""
 
+  __slots__ = ["_device_name", "_ctx", "_stack"]
+
   def __init__(self, ctx, device_name):
     self._device_name = device_name
     self._ctx = ctx

tensorflow/python/eager/def_function.py

@@ -54,6 +54,8 @@ FREQUENT_TRACING_WARNING_THRESHOLD = 5
 class _CallCounter(object):
   """Class keeping track of how many recent calls triggered tracing."""
 
+  __slots__ = ["_max_call_history", "_calls_per_tracings", "call_count"]
+
   def __init__(self, max_call_history):
     self._max_call_history = max_call_history
     self._calls_per_tracings = []
@@ -84,6 +86,8 @@ class _CallCounter(object):
 class _FrequentTracingDetector(object):
   """Class for frequent retracing detection and warning."""
 
+  __slots__ = ["_counters", "_lock"]
+
   def __init__(self):
     self._counters = weakref.WeakKeyDictionary()  # GUARDED_BY(self._lock)
     self._lock = threading.Lock()
@@ -428,6 +432,8 @@ def functions_run_eagerly():
 
 class FunctionDeleter(object):
 
+  __slots__ = ["func_graph"]
+
   def __init__(self, func_graph):
     self.func_graph = func_graph
 

tensorflow/python/eager/executor.py

@@ -40,6 +40,8 @@ class Executor(object):
   ```
   """
 
+  __slots__ = ["_handle"]
+
   def __init__(self, handle):
     self._handle = handle
 

tensorflow/python/eager/function.py

@@ -262,6 +262,8 @@ def _parse_func_attrs(attributes):
 class _InterpolateFunctionError(object):
   """Context Manager that interpolates the exception from 'top_level_func'."""
 
+  __slots__ = ["_func"]
+
   def __init__(self, top_level_func):
     self._func = top_level_func
 
@@ -378,6 +380,8 @@ def _enclosing_xla_context():
 class _EagerDefinedFunctionDeleter(object):
   """Unregister function from eager context."""
 
+  __slots__ = ["name"]
+
   def __init__(self, name):
     self.name = name
 
@@ -1410,6 +1414,9 @@ _POSSIBLE_GRADIENT_TYPES_HIGHER_ORDER = 2
 class _ForwardBackwardCall(object):
   """Holds the state of a function call between execution and recording."""
 
+  __slots__ = ["_functions", "_inference_args", "_input_tangents",
+               "_tape_watching"]
+
   def __init__(self, functions, inference_args, input_tangents, tape_watching):
     """Collects information about the function call.
 
@@ -2740,6 +2747,9 @@ class FunctionCache(object):
   """A lightweight container for cached functions.
   """
 
+  __slots__ = ["missed", "primary", "arg_relaxed_specs",
+               "arg_relaxed", "_garbage_collectors"]
+
   def __init__(self):
     # The set of functions that have been missed; entries are CacheKey with
     # input_signature `None` (e.g. a "call context key")
@@ -3771,6 +3781,8 @@ def class_method_to_instance_method(original_function, instance):
 class _FunctionGarbageCollector(object):
   """Cleans up cycles when a defun goes out of scope."""
 
+  __slots__ = ["_cache"]
+
   def __init__(self, cache):
     self._cache = cache
 
@@ -3788,6 +3800,8 @@ class _FunctionGarbageCollector(object):
 class ConcreteFunctionGarbageCollector(object):
   """Cleans up reference cycles when a `ConcreteFunction` goes out of scope."""
 
+  __slots__ = ["_func_graph"]
+
   def __init__(self, func_graph):
     self._func_graph = func_graph
 
@@ -3807,6 +3821,8 @@ class ConcreteFunctionGarbageCollector(object):
 class _Marker(object):
   """Markers used to pretty-print nested args in function signatures."""
 
+  __slots__ = ["_s"]
+
   def __init__(self, s):
     self._s = s
 

tensorflow/python/eager/monitoring.py

@@ -104,6 +104,8 @@ _sampler_methods = [
 class Metric(object):
   """The base class of metric."""
 
+  __slots__ = ["_metric", "_metric_name", "_metric_methods", "_label_length"]
+
   def __init__(self, metric_name, metric_methods, label_length, *args):
     """Creates a new metric.
 
@@ -145,6 +147,8 @@ class Metric(object):
 class CounterCell(object):
   """CounterCell stores each value of a Counter."""
 
+  __slots__ = ["_cell"]
+
   def __init__(self, cell):
     """Creates a new CounterCell.
 
@@ -174,6 +178,8 @@ class Counter(Metric):
   user to increment each value.
   """
 
+  __slots__ = []
+
   def __init__(self, name, description, *labels):
     """Creates a new Counter.
 
@@ -193,6 +199,8 @@ class Counter(Metric):
 class IntGaugeCell(object):
   """A single integer value stored in an `IntGauge`."""
 
+  __slots__ = ["_cell"]
+
   def __init__(self, cell):
     """Creates a new IntGaugeCell.
 
@@ -222,6 +230,8 @@ class IntGauge(Metric):
   allows the user to set each value.
   """
 
+  __slots__ = []
+
   def __init__(self, name, description, *labels):
     """Creates a new IntGauge.
 
@@ -241,6 +251,8 @@ class IntGauge(Metric):
 class StringGaugeCell(object):
   """A single string value stored in an `StringGauge`."""
 
+  __slots__ = ["_cell"]
+
   def __init__(self, cell):
     """Creates a new StringGaugeCell.
 
@@ -273,6 +285,8 @@ class StringGauge(Metric):
   allows the user to set each value.
   """
 
+  __slots__ = []
+
   def __init__(self, name, description, *labels):
     """Creates a new StringGauge.
 
@@ -292,6 +306,8 @@ class StringGauge(Metric):
 class BoolGaugeCell(object):
   """A single boolean value stored in an `BoolGauge`."""
 
+  __slots__ = ["_cell"]
+
   def __init__(self, cell):
     """Creates a new BoolGaugeCell.
 
@@ -321,6 +337,8 @@ class BoolGauge(Metric):
   allows the user to set each value.
   """
 
+  __slots__ = []
+
   def __init__(self, name, description, *labels):
     """Creates a new BoolGauge.
 
@@ -340,6 +358,8 @@ class BoolGauge(Metric):
 class SamplerCell(object):
   """SamplerCell stores each value of a Sampler."""
 
+  __slots__ = ["_cell"]
+
   def __init__(self, cell):
     """Creates a new SamplerCell.
 
@@ -373,6 +393,8 @@ class SamplerCell(object):
 class Buckets(object):
   """Bucketing strategies for the samplers."""
 
+  __slots__ = ["buckets"]
+
   def __init__(self, buckets):
     """Creates a new Buckets.
 
@@ -393,6 +415,8 @@ class ExponentialBuckets(Buckets):
        scale * growth_factor^(i + 1), ..., DBL_MAX].
   """
 
+  __slots__ = []
+
   def __init__(self, scale, growth_factor, bucket_count):
     """Creates a new exponential Buckets.
 
@@ -415,6 +439,8 @@ class Sampler(Metric):
   user to add a sample to each histogram value.
   """
 
+  __slots__ = []
+
   def __init__(self, name, buckets, description, *labels):
     """Creates a new Sampler.
 
@@ -435,6 +461,8 @@ class Sampler(Metric):
 class MonitoredTimer(object):
   """A context manager to measure the walltime and increment a Counter cell."""
 
+  __slots__ = ["cell", "t"]
+
   def __init__(self, cell):
     """Creates a new MonitoredTimer.
 

tensorflow/python/eager/tape.py

@@ -35,6 +35,8 @@ distribution_strategy_context = LazyLoader(
 class Tape(object):
   """Represents a gradient propagation trace."""
 
+  __slots__ = ["_tape"]
+
   def __init__(self, tape):
     self._tape = tape
 
@@ -72,6 +74,8 @@ class VariableWatcher(object):
   assert variable_watcher.watched_variables == [var]
   """
 
+  __slots__ = ["_variable_watcher"]
+
   def __init__(self):
     self._variable_watcher = None
 

tensorflow/python/framework/auto_control_deps.py

@@ -175,6 +175,9 @@ class AutomaticControlDependencies(object):
   NOT THREAD SAFE
   """
 
+  __slots__ = ["_returned_tensors", "ops_which_must_run", "_graph",
+               "_n_operations", "collective_manager_ids_used"]
+
   def __init__(self):
     self._returned_tensors = object_identity.ObjectIdentitySet()
     self.ops_which_must_run = set()

tensorflow/python/framework/c_api_util.py

@@ -29,6 +29,8 @@ from tensorflow.python.util import tf_contextlib
 class ScopedTFStatus(object):
   """Wrapper around TF_Status that handles deletion."""
 
+  __slots__ = ["status"]
+
   def __init__(self):
     self.status = c_api.TF_NewStatus()
 
@@ -42,6 +44,8 @@ class ScopedTFStatus(object):
 class ScopedTFGraph(object):
   """Wrapper around TF_Graph that handles deletion."""
 
+  __slots__ = ["graph", "deleter"]
+
   def __init__(self):
     self.graph = c_api.TF_NewGraph()
     # Note: when we're destructing the global context (i.e when the process is
@@ -57,6 +61,8 @@ class ScopedTFGraph(object):
 class ScopedTFImportGraphDefOptions(object):
   """Wrapper around TF_ImportGraphDefOptions that handles deletion."""
 
+  __slots__ = ["options"]
+
   def __init__(self):
     self.options = c_api.TF_NewImportGraphDefOptions()
 
@@ -70,6 +76,8 @@ class ScopedTFImportGraphDefOptions(object):
 class ScopedTFImportGraphDefResults(object):
   """Wrapper around TF_ImportGraphDefOptions that handles deletion."""
 
+  __slots__ = ["results"]
+
   def __init__(self, results):
     self.results = results
 
@@ -83,6 +91,8 @@ class ScopedTFImportGraphDefResults(object):
 class ScopedTFFunction(object):
   """Wrapper around TF_Function that handles deletion."""
 
+  __slots__ = ["func", "deleter"]
+
   def __init__(self, func):
     self.func = func
     # Note: when we're destructing the global context (i.e when the process is
@@ -100,6 +110,8 @@ class ScopedTFFunction(object):
 class ScopedTFBuffer(object):
   """An internal class to help manage the TF_Buffer lifetime."""
 
+  __slots__ = ["buffer"]
+
   def __init__(self, buf_string):
     self.buffer = c_api.TF_NewBufferFromString(compat.as_bytes(buf_string))
 
@@ -114,6 +126,8 @@ class ApiDefMap(object):
   be queried by op name.
   """
 
+  __slots__ = ["_api_def_map", "_op_per_name"]
+
   def __init__(self):
     op_def_proto = op_def_pb2.OpList()
     buf = c_api.TF_GetAllOpList()

tensorflow/python/framework/device.py

@@ -112,6 +112,8 @@ class MergeDevice(object):
   performance of device placement.
   """
 
+  __slots__ = ["_spec"]
+
   def __init__(self, spec):
     if isinstance(spec, device_spec.DeviceSpecV2):
       self._spec = spec

tensorflow/python/framework/function.py

@@ -194,6 +194,8 @@ class Defun(object):
 class _DefinedFunctionDeleter(object):
   """Unregister function from eager context."""
 
+  __slots__ = ["name"]
+
   def __init__(self, name):
     self.name = name
 

tensorflow/python/framework/ops.py

@@ -2583,6 +2583,8 @@ class RegisterGradient(object):
   that defines the operation.
   """
 
+  __slots__ = ["_op_type"]
+
   def __init__(self, op_type):
     """Creates a new decorator with `op_type` as the Operation type.
 
@@ -2679,6 +2681,8 @@ class OpStats(object):
 
   """
 
+  __slots__ = ["_statistic_type", "_value"]
+
   def __init__(self, statistic_type, value=None):
     """Sets up the initial placeholders for the statistics."""
     self.statistic_type = statistic_type
@@ -2758,6 +2762,8 @@ class RegisterStatistics(object):
 
   """
 
+  __slots__ = ["_op_type", "_statistic_type"]
+
   def __init__(self, op_type, statistic_type):
     """Saves the `op_type` as the `Operation` type."""
     if not isinstance(op_type, six.string_types):
@@ -5176,6 +5182,8 @@ class enable_auto_cast_variables(object):
   `dtype` is floating-point. Otherwise, `AutoCastVariable`s will not be cast.
   """
 
+  __slots__ = ["_dtype", "_graph", "_prev_read_dtype"]
+
   def __init__(self, dtype, graph=None):
     if dtype and not dtype.is_floating:
       self._dtype = None
@@ -6529,6 +6537,8 @@ class name_scope_v1(object):  # pylint: disable=invalid-name
   ```
   """
 
+  __slots__ = ["_name", "_name_scope"]
+
   @property
   def name(self):
     return self._name
@@ -6582,6 +6592,8 @@ class name_scope_v2(object):
   will generate `MyOp_1/a`, etc.
   """
 
+  __slots__ = ["_name", "_exit_fns"]
+
   def __init__(self, name):
     """Initialize the context manager.
 
@@ -6918,6 +6930,8 @@ def _reconstruct_sequence_inputs(op_def, inputs, attrs):
 class _TensorIterator(object):
   """Iterates over the leading dim of a Tensor. Performs no error checks."""
 
+  __slots__ = ["_tensor", "_index", "_limit"]
+
   def __init__(self, tensor, dim0):
     self._tensor = tensor
     self._index = 0

tensorflow/python/framework/registry.py

@@ -36,6 +36,8 @@ _TYPE_TAG = "type"
 class Registry(object):
   """Provides a registry for saving objects."""
 
+  __slots__ = ["_name", "_registry"]
+
   def __init__(self, name):
     """Creates a new registry."""
     self._name = name

tensorflow/python/framework/subscribe.py

@@ -67,6 +67,8 @@ def _recursive_apply(tensors, apply_fn):
 class _ControlOutputCache(object):
   """Helper class to manage calculating and caching control_outputs in graph."""
 
+  __slots__ = ["cache"]
+
   def __init__(self):
     self.cache = {}
 

tensorflow/python/keras/engine/input_spec.py

@@ -54,6 +54,8 @@ class InputSpec(object):
           a specific dimension value.
   """
 
+  __slots__ = ['dtype', 'shape', 'ndim', 'max_ndim', 'min_ndim', 'axes']
+
   def __init__(self,
                dtype=None,
                shape=None,

tensorflow/python/keras/mixed_precision/experimental/loss_scale_optimizer.py

@@ -49,6 +49,8 @@ class _UnwrapPreventer(object):
   unwrapped by DistributionStrategy
   """
 
+  __slots__ = ["value"]
+
   def __init__(self, value):
     self.value = value
 

tensorflow/python/ops/parallel_for/pfor.py

@@ -719,6 +719,8 @@ class ConversionNotImplementedError(Exception):
 class _PforInput(object):
   """Input object passed to registered pfor converters."""
 
+  __slots__ = ["pfor", "_op", "_inputs"]
+
   def __init__(self, pfor, op, inputs):
     """Creates a _PforInput object.
 

tensorflow/python/ops/resource_variable_ops.py

@@ -265,6 +265,8 @@ class EagerResourceDeleter(object):
   the cycle will be collectable.
   """
 
+  __slots__ = ["_handle", "_handle_device", "_context"]
+
   def __init__(self, handle, handle_device):
     if not isinstance(handle, ops.Tensor):
       raise ValueError(

tensorflow/python/ops/variable_scope.py

@@ -63,6 +63,8 @@ _api_usage_gauge = monitoring.BoolGauge(
 class _PartitionInfo(object):
   """Holds partition info used by initializer functions."""
 
+  __slots__ = ["_full_shape", "_var_offset"]
+
   def __init__(self, full_shape, var_offset):
     """Constructor.
 
@@ -279,6 +281,8 @@ class _VariableStore(object):
       the corresponding TensorFlow Variables as values.
   """
 
+  __slots__ = ["_vars", "_partitioned_vars", "_store_eager_variables"]
+
   def __init__(self):
     """Create a variable store."""
     self._vars = {}  # A dictionary of the stored TensorFlow variables.

tensorflow/python/training/saving/functional_saver.py

@@ -41,6 +41,8 @@ from tensorflow.python.util import nest
 class _SingleDeviceSaver(object):
   """Saves and restores checkpoints from the current device."""
 
+  __slots__ = ["_saveable_objects"]
+
   def __init__(self, saveable_objects):
     """Specify a list of `SaveableObject`s to save and restore.
 

tensorflow/python/training/session_manager.py

@@ -553,6 +553,8 @@ def _ready(op, sess, msg):
 
 class _CountDownTimer(object):
 
+  __slots__ = ["_start_time_secs", "_duration_secs"]
+
   def __init__(self, duration_secs):
     self._start_time_secs = time.time()
     self._duration_secs = duration_secs

tensorflow/python/training/tracking/base.py

@@ -190,6 +190,8 @@ class PythonStringStateSaveable(PythonStateSaveable):
 class CheckpointPosition(object):
   """Indicates a position within a `_CheckpointRestoreCoordinator`."""
 
+  __slots__ = ["_checkpoint", "_proto_id"]
+
   def __init__(self, checkpoint, proto_id):
     """Specify an object within a checkpoint.
 

tensorflow/python/training/tracking/data_structures.py

@@ -59,6 +59,8 @@ class NoDependency(object):
   variables will appear in `Model.variables`).
   """
 
+  __slots__ = ["value"]
+
   def __init__(self, value):
     self.value = value
 

tensorflow/python/training/tracking/tracking.py

@@ -140,6 +140,8 @@ def delete_tracking(obj, name):
 class ResourceTracker(object):
   """An object that tracks a list of resources."""
 
+  __slots__ = ["_resources"]
+
   def __init__(self):
     self._resources = []
 
@@ -183,6 +185,8 @@ def resource_tracker_scope(resource_tracker):
 class CapturableResourceDeleter(object):
   """Deleter to destroy CapturableResource without overriding its __del__()."""
 
+  __slots__ = ["_destruction_context", "_destroy_resource"]
+
   def __init__(self, destroy_resource_fn=None):
     if destroy_resource_fn:
       self._destroy_resource = destroy_resource_fn

tensorflow/python/training/tracking/util.py

@@ -86,6 +86,8 @@ class _ObjectGraphProtoPrettyPrinter(object):
   repeated naming is cheap after the first.
   """
 
+  __slots__ = ["_object_graph_proto", "_node_name_cache"]
+
   def __init__(self, object_graph_proto):
     self._object_graph_proto = object_graph_proto
     self._node_name_cache = None
@@ -124,6 +126,9 @@ class _ObjectGraphProtoPrettyPrinter(object):
 class _CheckpointRestoreCoordinatorDeleter(object):
   """Deleter to avoid overriding _CheckpointRestoreCoordinator.__del__()."""
 
+  __slots__ = ["expect_partial", "object_graph_proto",
+               "matched_proto_ids", "unused_attributes"]
+
   def __init__(self, expect_partial, object_graph_proto, matched_proto_ids,
                unused_attributes):
     self.expect_partial = expect_partial

tensorflow/python/util/lock_util.py

@@ -51,6 +51,8 @@ class GroupLock(object):
   can also use the `acquire` and `release` method directly.
   """
 
+  __slots__ = ["_ready", "_num_groups", "_group_member_counts"]
+
   def __init__(self, num_groups=2):
     """Initialize a group lock.
 
@@ -116,6 +118,8 @@ class GroupLock(object):
   class _Context(object):
     """Context manager helper for `GroupLock`."""
 
+    __slots__ = ["_lock", "_group_id"]
+
     def __init__(self, lock, group_id):
       self._lock = lock
       self._group_id = group_id

tensorflow/python/util/nest.py

@@ -344,6 +344,8 @@ _same_namedtuples = _pywrap_utils.SameNamedtuples
 
 class _DotString(object):
 
+  __slots__ = []
+
   def __str__(self):
     return "."
 

tensorflow/python/util/object_identity.py

@@ -122,6 +122,8 @@ class ObjectIdentityDictionary(collections_abc.MutableMapping):
   and comparing based on the equality of their contents by default).
   """
 
+  __slots__ = ["_storage"]
+
   def __init__(self):
     self._storage = {}
 
@@ -171,6 +173,8 @@ class ObjectIdentityWeakKeyDictionary(ObjectIdentityDictionary):
 class ObjectIdentitySet(collections_abc.MutableSet):
   """Like the built-in set, but compares objects with "is"."""
 
+  __slots__ = ["_storage"]
+
   def __init__(self, *args):
     self._storage = set(self._wrap_key(obj) for obj in list(*args))