code: def extra_downloader_converter(value):
      
      if isinstance(value, six.string_types):
          value = value.split(" ")
      return value
docs: Parses extra_{downloader,converter} arguments.
  
      Parameters
      ----------
      value : iterable or str
          If the value is a string, it is split into a list using spaces
          as delimiters. Otherwise, it is returned as is.