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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 to_call_agraph(self):
 """ Build a PyGraphviz AGraph object corresponding to a call graph of functions. """


        A = nx.nx_agraph.to_agraph(self.call_graph)
        A.graph_attr.update({"dpi": 227, "fontsize": 20, "fontname": "Menlo"})
        A.node_attr.update(
            {"shape": "rectangle", "color": "#650021", "style": "rounded"}
        )
        A.edge_attr.update({"color": "#650021", "arrowsize": 0.5})
        return A