class_docstr: An intermediate representation for DL graph.
code: def as_graph_def(self):
      graph_pb2 = GraphDef()
      graph_pb2.version = self.version
      graph_pb2.node.extend(
          [node.node_pb2 for node in self.node_dict.values()]
      )
      return graph_pb2
  
imports: import six
  from six import string_types
  from mmdnn.conversion.caffe.errors import ConversionError
  from mmdnn.conversion.common.IR.graph_pb2 import GraphDef, NodeDef, TensorShape
  from mmdnn.conversion.caffe.utils import get_real_name
label_desc: Use image node_id 7 for calling the Graph obj's underlying member method code with example usage: obj.as_graph_def() and returns: graph_pb2