def decapitalize(string: str) -> str:
    """
    Decapitalize a string.

    Returns:
        [type]: Decapitalized string.

    >>> decapitalize('a')
    'a'

    >>> decapitalize('A')
    'a'

    >>> decapitalize('Ab')
    'ab'

    >>> decapitalize('AB')
    'aB'
    """
    if len(string) <= 1:
        return string.lower()

    return string[0].lower() + string[1:]