code: def coord_pyramid(coord, zoom_start, zoom_stop):
      
      if zoom_start <= coord.zoom:
          yield coord
      for child_coord in coord_children_range(coord, zoom_stop):
          if zoom_start <= child_coord.zoom:
              yield child_coord
docs: generate full pyramid for coord
  
      Generate the full pyramid for a single coordinate. Note that zoom_stop is
      exclusive.