 a scalar is returned.
            If True, the result has dimension with size one along the reduced axis.

            .. versionadded:: 2.1

               This parameter is not required in the _reduce signature to keep backward
               compatibility, but will become required in the future. If the parameter
               is not found in the method signature, a FutureWarning will be emitted.
        **kwargs
            Additional keyword arguments passed to the reduction function.
            Currently, `ddof` is the only supported kwarg.

        Returns
        -------
        scalar

        Raises
        ------
        TypeError : subclass does not define reductions

        Examples
        --------
        >>> pd.array([1, 2, 3])._reduce("min")
        1
        Nú