def checkdist(conddist):
    """
    Check user input type if distribution type selected for generating conditions.

    Parameters
    ----------
    conddist : str or NoneType
        condition distribution name

    Returns
    -------
    str or None
    """
    if  conddist is None:
        return None
    elif conddist.lower() == 'none' or conddist == '':
        return None
    elif conddist.lower() == 'r' or conddist.lower() == 'random':
        return 'random'
    elif conddist.lower() == 'v' or conddist.lower() == 'variant':
        return 'variant'
    else:
        print(' ValueError: Condition distribution type \'{}\' not recognized.'.format(conddist))
        print(' Conditions distributions must be "r", "random", "v", or "variant".')
        raise ValueError