code: def add_statement(self,statement_obj):
          
          if self.attribution_layer is None:
              self.attribution_layer = Cattribution()
              self.root.append(self.attribution_layer.get_node())
          self.attribution_layer.add_statement(statement_obj)
docs: Adds a statement to the attribution layer
          @type statement_obj: L{Cstatement}
          @param statement_obj: the statement object