Fix graph text format serialization

PiperOrigin-RevId: 157669530

tensorflow/python/framework/graph_io.py

@@ -21,6 +21,7 @@ from __future__ import print_function
 import os
 import os.path
 
+from google.protobuf import text_format
 from tensorflow.python.framework import ops
 from tensorflow.python.lib.io import file_io
 
@@ -64,7 +65,8 @@ def write_graph(graph_or_graph_def, logdir, name, as_text=True):
     file_io.recursive_create_dir(logdir)
   path = os.path.join(logdir, name)
   if as_text:
-    file_io.atomic_write_string_to_file(path, str(graph_def))
+    file_io.atomic_write_string_to_file(path,
+                                        text_format.MessageToString(graph_def))
   else:
     file_io.atomic_write_string_to_file(path, graph_def.SerializeToString())
   return path