docs: def fetch_all_droplets(self, tag_name=None):
          r"""
          Returns a generator that yields all of the droplets belonging to the
          account
  
          .. versionchanged:: 0.2.0
              ``tag_name`` parameter added
  
          :param tag_name: if non-`None`, only droplets with the given tag are
              returned
          :type tag_name: string or `Tag`
          :rtype: generator of `Droplet`\ s
          :raises DOAPIError: if the API endpoint replies with an error
          """
          params = {}
          if tag_name is not None:
              params["tag_name"] = str(tag_name)
          return map(self._droplet, self.paginate('/v2/droplets', 'droplets',
                                                  params=params))