<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _validate(self, writing=False):
 """ Validate the box before writing to file. """

        if self.brand not in ['jp2 ', 'jpx ']:
            msg = ("The file type brand was '{brand}'.  "
                   "It should be either 'jp2 ' or 'jpx '.")
            msg = msg.format(brand=self.brand)
            if writing:
                raise IOError(msg)
            else:
                warnings.warn(msg, UserWarning)
        for item in self.compatibility_list:
            if item not in self._valid_cls:
                msg = ("The file type compatibility list {items} is "
                       "not valid.  All items should be members of "
                       "{valid_entries}.")
                msg = msg.format(items=self.compatibility_list,
                                 valid_entries=self._valid_cls)
                if writing:
                    raise IOError(msg)
                else:
                    warnings.warn(msg, UserWarning)