@staticmethod
def equal(series1, series2):
    """Check equality - same instance.

        Parameters
        ----------
        series1 : TimeSeries
            A time series
        series2 : TimeSeries
            Another time series

        Returns
        -------
        bool
            Are the two the same instance?
        """
    return bool(series1._data is series2._data and series1._collection is
        series2._collection)
