@c-bata, @porink0424 Could you review this PR?

Could you show us the correspondence of the arguments between download_artifact and upload_artifact , please?

@toshihikoyanase
The current API for each function looks like this:

def upload_artifact(study_or_trial, file_path, artifact_store, ...) -> str:
    ...

def download_artifact(artifact_store, artifact_id, file_path) -> None:
    ...

I updated download_artifact to:

def download_artifact(file_path, artifact_store, artifact_id) -> None:
    ...

so that file_path comes before artifact_store for both functions.
Another possibility is to make them:

def upload_artifact(artifact_store, file_path, study_or_trial,  ...) -> str:
    ...

def download_artifact(artifact_store, file_path, artifact_id) -> None:
    ...

Although this change makes the order clearer, it will be a breaking change.
I avoided the breaking change in this PR, but what do you think, @c-bata ?