code: def graphHasField(self, graph_name, field_name):
          
          graph = self._graphDict.get(graph_name, True)
          return graph.hasField(field_name)
docs: Return true if graph with name graph_name has field with 
          name field_name.
          
          @param graph_name: Graph Name
          @param field_name: Field Name.
          @return: Boolean