<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _clean_file_name(self, model_instance, filename):
 """ We need to make sure we know the full file name before we save the thumbnail so we can be sure the name doesn't change on save. This method gets the available filename and returns just the file part. """

        available_name = self.storage.get_available_name(
            self.generate_filename(model_instance, filename))
        return os.path.basename(available_name)