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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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):
 """

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