Generate a sif file from the call map

def genenare_callmap_sif(self, filepath):
        """
        Generate a sif file from the call map
        """
        graph = self.call_map

        if graph is None:
            raise AngrGirlScoutError('Please generate the call graph first.')

        f = open(filepath, "wb")

        for src, dst in graph.edges():
            f.write("0x%x\tDirectEdge\t0x%x\n" % (src, dst))

        f.close()