def METHOD_NAME(string):
    """
    Removes/substitutes characters in a string to make it suitable as a username value
    Args:
        string (str): A string
    Returns:
        str: A version of the string with username-appropriate characters
    """
    cleaned_string = re.sub(USERNAME_INVALID_CHAR_PATTERN, "", string)
    cleaned_string = re.sub(
        USERNAME_TURKISH_I_CHARS, USERNAME_TURKISH_I_CHARS_REPLACEMENT, cleaned_string
    )
    return (
        re.sub(USERNAME_SEPARATOR_REPLACE_PATTERN, USERNAME_SEPARATOR, cleaned_string)
        .lower()
        .strip(USERNAME_SEPARATOR)
    )