code: def _validate_edge_fields_are_all_none(graph):
      if not all(
          getattr(graph, x) is None for x in [EDGES, RECEIVERS, SENDERS]
      ):
          raise ValueError(
              "Can only add fully connected a graph with `None`"
              "edges, receivers and senders"
          )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import functools
  from absl import logging
  from graph_nets import graphs
  from graph_nets import utils_np
  import six
  from six.moves import range
  import tensorflow
  import tree
label_desc: Use image node_id 19 for calling a global function with example usage: _validate_edge_fields_are_all_none(graph) without return types