<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def whisper_filename(self):
 """Build a file path to the Whisper database"""

        source_name = self.source_id and self.source.name or ''
        return get_valid_filename("{0}__{1}.wsp".format(source_name,
                                                        self.name))