<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _save_metadata(self):
 """ Write this prefix metadata to disk Returns: None """

        with open(self.paths.metadata(), 'w') as metadata_fd:
            utils.json_dump(self.metadata, metadata_fd)