<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_empty(self):
        '''Returns True if all titleInfo subfields are not set or
        empty; returns False if any of the fields are not empty.'''
        return not bool(self.title or self.subtitle or self.part_number \
                        or self.part_name or self.non_sort or self.type)