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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def s3_etag(url: str) -> Optional[str]: """Check ETag on S3 object."""

    s3_resource = boto3.resource("s3")
    bucket_name, s3_path = split_s3_path(url)
    s3_object = s3_resource.Object(bucket_name, s3_path)
    return s3_object.e_tag