def xr_size(
    da):
    """
    Description:
        Returns the size of a xarray.Dataset or xarray.DataArray object in
        Gigabytes GB, not Gibibytes (GiB)
    
    Parameters:
        da - xarray.Dataset or xarray.DataArray
    """

    return str(da.nbytes / (1000**3))+' gigabytes'