code: def getSubgraphFieldCount(self, parent_name, graph_name):
          
          graph = self._getSubGraph(parent_name, graph_name, True)
          return graph.getFieldCount()
docs: Returns number of fields for subgraph with name graph_name and parent 
          graph with name parent_name.
          
          @param parent_name: Root Graph Name
          @param graph_name:  Subgraph Name
          @return:            Number of fields for subgraph.