I'm creating a subclass of s3fs.S3FileSystem that connects to either AWS S3 or MinIO based on environment variables. The connection should fail immediately during initialization if credentials are invalid.

The parent class accepts invalid credentials during initialization, only failing later during actual operations (like ls() or file access).

When I try to validate the connection by calling self.ls('') inside __init__ (via a _test_connection() helper), I get a NotImplementedError. However, if I call the same method after instantiation, it works correctly.

class S3MinioConnector(s3fs.S3FileSystem):
    def __init__(self) -> None:
        # ... (setup code)
        super().__init__(**params)  # Initialize parent
        self._test_connection()    # Fails here with NotImplementedError

    def _test_connection(self):
        self.ls('')  # Inherited method

How can I properly validate the connection during initialization without:

• Getting NotImplementedError?

• Using obscure solutions like time.sleep(2)?