View the graph.

        Args:
          vleaf (`nnabla.Variable`): End variable. All variables and functions which can be traversed from this variable are shown in the reuslt.
          fpath (`str`): The file path used to save. 
          cleanup (`bool`): Clean up the source file after rendering. Default is True.
          format (str):
              Force overwrite ``format`` (``'pdf', 'png', ...)``) configuration.

def view(self, vleaf, fpath=None, cleanup=True, format=None):
        """View the graph.

        Args:
          vleaf (`nnabla.Variable`): End variable. All variables and functions which can be traversed from this variable are shown in the reuslt.
          fpath (`str`): The file path used to save. 
          cleanup (`bool`): Clean up the source file after rendering. Default is True.
          format (str):
              Force overwrite ``format`` (``'pdf', 'png', ...)``) configuration.

        """
        graph = self.create_graphviz_digraph(vleaf, format=format)
        graph.view(fpath, cleanup=cleanup)