<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def auth_delete_creds(self, username=None):
 		""" 		Delete the credentials for a specific username if specified or all 		stored credentials. 		:param str username: The username of the credentials to delete. 		"""

		if not username:
			self.__config['basic_auth'] = {}
			self.logger.info('basic authentication database has been cleared of all entries')
			return
		del self.__config['basic_auth'][username]