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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 backup(id):
 """Backup the database to S3."""

    filename = dump_database(id)
    key = "{}.dump".format(id)

    bucket = user_s3_bucket()
    bucket.upload_file(filename, key)
    return _generate_s3_url(bucket, key)