Adds Operations() method to Graph

There is currently no way to list all of the operations in a graph
from the go api. This patch ads an Operations() method to retrieve the
list using the existing TF_GraphNextOperation c api. The graph_test
was modified to include testing this new method.

Signed-off-by: Vishvananda Ishaya Abrams <vishvananda@gmail.com>

tensorflow/go/graph.go

@@ -114,6 +114,20 @@ func (g *Graph) Operation(name string) *Operation {
 	return &Operation{cop, g}
 }
 
+// Operations returns a list of all operations in the graph
+func (g *Graph) Operations() []Operation {
+	var pos C.size_t = 0
+	ops := []Operation{}
+	for {
+		cop := C.TF_GraphNextOperation(g.c, &pos)
+		if cop == nil {
+			break
+		}
+		ops = append(ops, Operation{cop, g})
+	}
+	return ops
+}
+
 // OpSpec is the specification of an Operation to be added to a Graph
 // (using Graph.AddOperation).
 type OpSpec struct {

tensorflow/go/graph_test.go

@@ -29,10 +29,26 @@ func hasOperations(g *Graph, ops ...string) error {
 			missing = append(missing, op)
 		}
 	}
-	if len(missing) == 0 {
-		return nil
+	if len(missing) != 0 {
+		return fmt.Errorf("Graph does not have the operations %v", missing)
 	}
-	return fmt.Errorf("Graph does not have the operations %v", missing)
+
+	inList := map[string]bool{}
+	for _, op := range g.Operations() {
+		inList[op.Name()] = true
+	}
+
+	for _, op := range ops {
+		if !inList[op] {
+			missing = append(missing, op)
+		}
+	}
+
+	if len(missing) != 0 {
+		return fmt.Errorf("Operations %v are missing from graph.Operations()", missing)
+	}
+
+	return nil
 }
 
 func TestGraphWriteToAndImport(t *testing.T) {