Find the last <instr> in the block from start to end.
        <instr> is any python bytecode instruction or a list of opcodes
        If <instr> is an opcode with a target (like a jump), a target
        destination can be specified which must match precisely if exact
        is True, or if exact is False, the instruction which has a target
        closest to <target> will be returned.

        Return index to it or None if not found.

def last_instr(self, start, end, instr, target=None, exact=True):
        """
        Find the last <instr> in the block from start to end.
        <instr> is any python bytecode instruction or a list of opcodes
        If <instr> is an opcode with a target (like a jump), a target
        destination can be specified which must match precisely if exact
        is True, or if exact is False, the instruction which has a target
        closest to <target> will be returned.

        Return index to it or None if not found.
        """

        code = self.code
        # Make sure requested positions do not go out of
        # code bounds
        if not (start >= 0 and end <= len(code)):
            return None

        try:
            None in instr
        except:
            instr = [instr]

        result_offset = None
        current_distance = self.insts[-1].offset - self.insts[0].offset
        extended_arg = 0
        # FIXME: use self.insts rather than code[]
        for offset in self.op_range(start, end):
            op = code[offset]

            if op == self.opc.EXTENDED_ARG:
                arg = code2num(code, offset+1) | extended_arg
                extended_arg = extended_arg_val(self.opc, arg)
                continue

            if op in instr:
                if target is None:
                    result_offset = offset
                else:
                    dest = self.get_target(offset, extended_arg)
                    if dest == target:
                        current_distance = 0
                        result_offset = offset
                    elif not exact:
                        new_distance = abs(target - dest)
                        if new_distance <= current_distance:
                            current_distance = new_distance
                            result_offset = offset
                            pass
                        pass
                    pass
                pass
            extended_arg = 0
            pass
        return result_offset