code: def setGraphVal(self, graph_name, field_name, val):
          
          graph = self._getGraph(graph_name, True)
          if graph.hasField(field_name):
              graph.setVal(field_name, val)
          else:
              raise AttributeError("Invalid field name %s for graph %s." 
                                   % (field_name, graph_name))
docs: Utility method to set Value for Field in Graph.
          
          The private method is for use in retrieveVals() method of child classes.
          
          @param graph_name: Graph Name
          @param field_name: Field Name.
          @param val:        Value for field.