<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_gaf_format(self):
 """Return a GAF 2.0-compatible string representation of the annotation. Parameters Returns ------- str The formatted string. """

        sep = '\t'
        return sep.join(
            [self.gene, self.db_ref, self.term.id, self.evidence,
             '|'.join(self.db_ref), '|'.join(self.with_)])