def sort_ballot(ballot):
    """Put a ballot in alphabetical order.

    Parameters
    ----------
    ballot : str
        A ballot, e.g. ``'a'``, ``'ab'``, ``'ba'``, etc.

    Returns
    -------
    str
        The same ballot in alphabetical order.

    Examples
    --------
        >>> sort_ballot('a')
        'a'
        >>> sort_ballot('ab')
        'ab'
        >>> sort_ballot('ba')
        'ab'
    """
    return ''.join(sorted(ballot))
