Return the number of data points up to and including the
        provided day.

def data_len_for_day(self, day):
        """
        Return the number of data points up to and including the
        provided day.
        """
        day_ix = self._session_labels.get_loc(day)
        # Add one to the 0-indexed day_ix to get the number of days.
        num_days = day_ix + 1
        return num_days * self._minutes_per_day