code: def test_concatenate_data_dicts(self):
      cat = utils_np._concatenate_data_dicts(self.graphs_dicts_in)
      for k, v in cat.items():
          self.assertAllEqual(getattr(self.reference_graph, k), v)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import itertools
  from absl.testing import parameterized
  from graph_nets import utils_np
  from graph_nets.tests import test_utils
  import networkx
  import numpy
  from six.moves import range
  import tensorflow
label_desc: Use image node_id 2 for calling the ConcatenationTest obj's underlying member method code with example usage: obj.test_concatenate_data_dicts() without return types