Directed graph with edges from knob residue to each hole residue for each KnobIntoHole in self.

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