docs: def row_generator(resource, doc, env, *args, **kwargs):
      """ An example row generator function.
  
      Reference this function in a Metatab file as the value of a Datafile:
  
              Datafile: python:pylib#row_generator
  
      The function must yield rows, with the first being headers, and subsequenct rows being data.
  
      :param resource: The Datafile term being processed
      :param doc: The Metatab document that contains the term being processed
      :param args: Positional arguments passed to the generator
      :param kwargs: Keyword arguments passed to the generator
      :return:
  
  
      The env argument is a dict with these environmental keys:
  
      * CACHE_DIR
      * RESOURCE_NAME
      * RESOLVED_URL
      * WORKING_DIR
      * METATAB_DOC
      * METATAB_WORKING_DIR
      * METATAB_PACKAGE
  
      It also contains key/value pairs for all of the properties of the resource.
  
      """
  
      yield 'a b c'.split()
  
      for i in range(10):
          yield [i, i*2, i*3]