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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 get_user_id(user_id_or_username):
 """Gets the user ID based on the value `user_id_or_username` specified on the command-line, being extra lenient and lowercasing the value in all cases. """

    user_id_or_username = user_id_or_username.lower()
    if not user_id_or_username.startswith("user-"):
        user_id = "user-" + user_id_or_username.lower()
    else:
        user_id = user_id_or_username
    return user_id