code: def sort_coords(coord):
      
      import iris
      order = {'T': -2, 'Z': -1, 'X': 1, 'Y': 2}
      axis = iris.util.guess_coord_axis(coord)
      return (order.get(axis, 0), coord and coord.name())
docs: Sorts a list of DimCoords trying to ensure that
      dates and pressure levels appear first and the
      longitude and latitude appear last in the correct
      order.