def METHOD_NAME(self):
    if self.op is None and self.arg.isdigit():
        value = int(self.arg)     # non-negative: '-' not in self.arg
        if value >= 2**31:
            raise OverflowError("cannot emit %r: limited to 2**31-1"
                                % (self.arg,))
        return format_four_bytes(value)
    if isinstance(self.arg, str):
        raise VerificationError("cannot emit to Python: %r" % (self.arg,))
    return format_four_bytes((self.arg << 8) | self.op)