code: def _add_nodes_edges(self, subj_agent, obj_agent, relation, evidences):
          
          subj_data, subj_edge = _get_agent_node(subj_agent)
          obj_data, obj_edge = _get_agent_node(obj_agent)
          # If we failed to create nodes for subject or object, skip it
          if subj_data is None or obj_data is None:
              return
          subj_node = self.model.add_node_from_data(subj_data)
          obj_node = self.model.add_node_from_data(obj_data)
          edge_data_list = \
              _combine_edge_data(relation, subj_edge, obj_edge, evidences)
          for edge_data in edge_data_list:
              self.model.add_edge(subj_node, obj_node, **edge_data)
docs: Given subj/obj agents, relation, and evidence, add nodes/edges.