def prepend(self, other: Self) -> Self:
        """
        Prepends (i.e. adds to the beginning) another series to this series along the time axis.

        Parameters
        ----------
        other
            A second TimeSeries.

        Returns
        -------
        TimeSeries
            A new TimeSeries, obtained by appending the second TimeSeries to the first.

        See Also
        --------
        Timeseries.append : append (i.e. add to the end) another series along the time axis.
        TimeSeries.concatenate : concatenate another series along a given axis.
        """
        raise_if_not(
            isinstance(other, self.__class__),
            f"`other` to prepend must be a {self.__class__.__name__} object.",
        )
        return other.append(self)

        Prepends (i.e. adds to the beginning) another series to this series along the time axis.

        Parameters
        ----------
        other
            A second TimeSeries.

        Returns
        -------
        TimeSeries
            A new TimeSeries, obtained by appending the second TimeSeries to the first.

        See Also
        --------
        Timeseries.append : append (i.e. add to the end) another series along the time axis.
        TimeSeries.concatenate : concatenate another series along a given axis.
        
darts/timeseries.py