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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 daisy_chain_graph(self):
 """ Directed graph with edges from knob residue to each hole residue for each KnobIntoHole in self. """

        g = networkx.DiGraph()
        for x in self.get_monomers():
            for h in x.hole:
                g.add_edge(x.knob, h)
        return g