def _interpolate(self, kind="linear", **kwargs) -> T_Xarray:
        """Apply scipy.interpolate.interp1d along resampling dimension."""
        obj = self._drop_coords()
        (grouper,) = self.groupers
        kwargs.setdefault("bounds_error", False)
        return obj.interp(
            coords={self._dim: grouper.full_index},
            assume_sorted=True,
            method=kind,
            kwargs=kwargs,
        )
Apply scipy.interpolate.interp1d along resampling dimension.
xarray/core/resample.py