@staticmethod
def _positive_tail_set(row):
    """
        Takes as input a row from the vol_adj_price DataFrame and then returns a list of names of the securites in the
        positive tail set, for this specific row date.

        This method is used in an apply() setting.

        :param row: (Series) of volatility adjusted prices.
        :return: (list) of securities in the positive tail set.
        """
    return list(row[row == 1].index)
