def _weighted_std(
        self,
        da: T_DataArray,
        dim: Dims = None,
        skipna: bool | None = None,
    ) -> T_DataArray:
        """Reduce a DataArray by a weighted ``std`` along some dimension(s)."""

        return cast("T_DataArray", np.sqrt(self._weighted_var(da, dim, skipna)))
Reduce a DataArray by a weighted ``std`` along some dimension(s).
xarray/computation/weighted.py