Ошибка пользовательской функции Django FileField upload_to

Я создал пользовательскую служебную функцию для параметра FileField в Django upload_to. Эта функция принимает префикс и возвращает функцию, которая фактически принимает instance и filename. Но когда я запускаю manage.py makemigrations, команда выбрасывает ValueError. Я включил соответствующие файлы/данные ниже.

secret_upload функция

import uuid

def secret_upload(prefix):
    def _path(instance, filename):
        file = filename.split(".")
        fuuid = uuid.uuid4()

        if len(file) == 1:
            filename = f"secrets/{prefix}/{file[0]}-{fuuid}"
        elif len(file) == 2:
            filename = f"secrets/{prefix}/{file[0]}-{fuuid}.{file[1]}"

        return filename

    return _path

Django Model

class SecretData(models.Model):
    name = models.CharField(max_length=100)
    secret_file = models.FileField(upload_to=secret_upload("files"))

makemigrations трассировка ошибки

 (most recent call last):
  File "D:\Python\projects\keep-creds\keep_creds\manage.py", line 22, in <module>
    main()
  File "D:\Python\projects\keep-creds\keep_creds\manage.py", line 18, in main
    execute_from_command_line(sys.argv)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\__init__.py", line 425, in execute_from_command_line
    utility.execute()
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\__init__.py", line 419, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\base.py", line 373, in run_from_argv
    self.execute(*args, **cmd_options)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\base.py", line 417, in execute
    output = self.handle(*args, **options)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\base.py", line 90, in wrapped
    res = handle_func(*args, **kwargs)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\commands\makemigrations.py", line 190, in handle
    self.write_migration_files(changes)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\core\management\commands\makemigrations.py", line 227, in write_migration_files
    migration_string = writer.as_string()
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\writer.py", line 141, in as_string
    operation_string, operation_imports = OperationWriter(operation).serialize()
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\writer.py", line 99, in serialize
    _write(arg_name, arg_value)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\writer.py", line 63, in _write
    arg_string, arg_imports = MigrationWriter.serialize(_arg_value)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\writer.py", line 271, in serialize
    return serializer_factory(value).serialize()
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\serializer.py", line 201, in serialize
    return self.serialize_deconstructed(path, args, kwargs)
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\serializer.py", line 88, in serialize_deconstructed
    arg_string, arg_imports = serializer_factory(arg).serialize()
  File "D:\Python\projects\kc-venv\lib\site-packages\django\db\migrations\serializer.py", line 160, in serialize
    raise ValueError(
ValueError: Could not find function _path in credentials.utils.

Какова возможная причина этого? Потому что _path определяется внутри.

    if '<' not in self.value.__qualname__:  # Qualname can include <locals>
        return '%s.%s' % (module_name, self.value.__qualname__), {'import %s' % self.value.__module__}
    
    raise ValueError(
        'Could not find function %s in %s.\n' % (self.value.__name__, module_name)
    )