@staticmethod
def clean_key(key):
    """
        Strips characters from the input key that have a special meaning to the configuration type.
        Namely '$' and '_'.

        :param key: (string) the key to strip special characters from
        :return: (string) the original or stripped key
        """
    if key.startswith('$') or key.startswith('_'):
        return key[1:]
    return key
