Get a particular instruction by using the address

        :param off: address of the instruction
        :type off: int

        :rtype: an :class:`Instruction` object

def get_ins_off(self, off):
        """
        Get a particular instruction by using the address

        :param off: address of the instruction
        :type off: int

        :rtype: an :class:`Instruction` object
        """
        idx = 0
        for i in self.get_instructions():
            if idx == off:
                return i
            idx += i.get_length()
        return None