@staticmethod
def simplify_tag(tag):
    """
        Maps part of speech (PoS) tag to a subset of PoS tags to better consolidate categorical labels.

        Parameters
        ----------
        tag : str
            The Penn-style PoS tag to be mapped to a simplified form.

        Returns
        -------
        str
            A simplified form of `tag`.  In some cases, the returned form may be identical to `tag`.
        """
    simple_tag = '"{}"'.format(tag)
    if tag.startswith('NNP'):
        simple_tag = '/^NNP/'
    elif tag.startswith('NN'):
        simple_tag = '/^N/'
    elif tag.startswith('VB'):
        simple_tag = '/^V/'
    elif tag.startswith('JJ'):
        simple_tag = '/^J/'
    elif tag.startswith('RB'):
        simple_tag = '/^RB/'
    elif tag.startswith('PRP'):
        simple_tag = '/^PRP/'
    elif tag == 'WDT':
        simple_tag = '/DT$/'
    elif tag == 'DT':
        simple_tag = '/DT$/'
    return simple_tag
