docs: def reload(filename=None,
          url=r"https://raw.githubusercontent.com/googlei18n/emoji4unicode/master/data/emoji4unicode.xml",
          loader_class=None):
      u"""reload google's `emoji4unicode` project's xml file. must call this method first to use `e4u` library."""
      if loader_class is None:
          loader_class = loader.Loader
      global _loader
      _loader = loader_class()
      _loader.load(filename, url)