def get_linenumbertable(self):
        """
        a sequence of (code_offset, line_number) pairs.

        reference: http://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.7.12
        """  # noqa

        lnt = self._lnt
        if lnt is None:
            buff = self.get_attribute("LineNumberTable")
            if buff is None:
                lnt = tuple()
            else:
                with unpack(buff) as up:
                    lnt = tuple(up.unpack_struct_array(_HH))
            self._lnt = lnt
        return lnt