code: def get_pydot_graph(self):
          
          rel = "is_a"
          # Initialize empty dag
          dag = pydot.Dot(graph_type='digraph', **self.kws['dag'])
          # Initialize nodes
          go2node = self._get_go2pydotnode()
          # Add nodes to graph
          for node in go2node.values():
              dag.add_node(node)
          # Add edges to graph
          rel2edgekws = self.rel2edgekws
          self.edgesobj.chk_edges()
          edgekws = rel2edgekws.get(rel)
          self._add_edges(self.edgesobj.edges, go2node, dag, **edgekws)
          for reltype, edges_list in self.edgesobj.edges_rel.items():
              edgekws = rel2edgekws.get(reltype)
              self._add_edges(edges_list, go2node, dag, **edgekws)
          return dag
docs: Given a DAG, return a pydot digraph object.