<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def extra(self, value, extra_name, default=None):
 """ Get the additional enumeration value for ``extra_name``. :param unicode value: Enumeration value. :param str extra_name: Extra name. :param default: Default value in the case ``extra_name`` doesn't exist. """

        try:
            return self.get(value).get(extra_name, default)
        except InvalidEnumItem:
            return default