Generate a sif file from the call map.

        :param filepath:    Path of the sif file
        :return:            None

def _genenare_callmap_sif(self, filepath):
        """
        Generate a sif file from the call map.

        :param filepath:    Path of the sif file
        :return:            None
        """
        with open(filepath, "wb") as f:
            for src, dst in self.callgraph.edges():
                f.write("%#x\tDirectEdge\t%#x\n" % (src, dst))