code: def edge(self, node1_id, node2_id, *args, **kwargs):
      self.events.append("add_edge")
      return super(MockedDigraph, self).edge(
          node1_id, node2_id, *args, **kwargs
      )
  
file_path: neupy/tests/layers/graph/test_visualizations.py
imports: import mock
  import tempfile
  import graphviz
  from neupy import layers
  from base import BaseTestCase
label_desc: Use image node_id 2 for calling the MockedDigraph obj's underlying member method code with example usage: obj.edge(node1_id, node2_id) and returns: super