code: def to_list(thing):
      if thing is None:
          return []
      if isinstance(thing, set):
          return list(thing)
      if isinstance(thing, types.StringTypes):
          if thing.startswith("["):
              return ast.literal_eval(thing)
      if not (is_list(thing) or is_tuple(thing)):
          return [thing]
      return list(thing)