# `part` represents a field/file received in a multipart request
async for part in request.files(max_file_size=16384):
    filename = part['filename']
    # ...
    # stream a (possibly) large part in chunks
    async for data in part.stream():
        # ...

    # NOTE: `part['data']` is `pop()`ed and
    # the second `stream()` call on the same `part` is a no-op
    async for data in part.stream():
        raise ValueError  # should not raised!

# `part` represents a field/file received in a multipart request
async for part in request.files(max_file_size=16384):
    filename = part['filename']
    # ...
    data = part['data']
    # ...
    if part['eof']:
        # end of a multipart field/file
    else:
        # this is a partial file