def key_check(v):
    """ Check that a keyword argument satisfies the form required of a
    keyword argument that checks frame types.

    Parameters
    ----------
    v : str
      value of a keyword argument

    Returns
    -------
    v : str, list
      A value used by the settings dictionary
    """
    text = v.strip().replace('_', ' ')
    if ',' in text and text[0:2] != '%,':
        # There are multiple possibilities - split the text
        v = text.split(',')
    else:
        v = text
    return v