docs: def get(map_name):
    """Get an instance of a map by name. Errors if the map doesn't exist."""
    if isinstance(map_name, Map):
      return map_name
  
    # Get the list of maps. This isn't at module scope to avoid problems of maps
    # being defined after this module is imported.
    maps = get_maps()
    map_class = maps.get(map_name)
    if map_class:
      return map_class()
    raise NoMapException("Map doesn't exist: %s" % map_name)