Group by supplied dimension(s) and overlay each group

        Groups data by supplied dimension(s) overlaying the groups
        along the dimension(s).

        Args:
            dimensions: Dimension(s) of dimensions to group by

        Returns:
            NdOverlay object(s) with supplied dimensions

def overlay(self, dimensions=None, **kwargs):
        """Group by supplied dimension(s) and overlay each group

        Groups data by supplied dimension(s) overlaying the groups
        along the dimension(s).

        Args:
            dimensions: Dimension(s) of dimensions to group by

        Returns:
            NdOverlay object(s) with supplied dimensions
        """
        dimensions = self._valid_dimensions(dimensions)
        if len(dimensions) == self.ndims:
            with item_check(False):
                return NdOverlay(self, **kwargs).reindex(dimensions)
        else:
            dims = [d for d in self.kdims if d not in dimensions]
            return self.groupby(dims, group_type=NdOverlay, **kwargs)