<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_set_on(self, xblock):
 """ Return whether this field has a non-default value on the supplied xblock """

        # pylint: disable=protected-access
        return self._is_dirty(xblock) or xblock._field_data.has(xblock, self.name)