code: def to_files(self, resource, directory):
          
          collections = self.__collect(resource)
          for (mb_cls, coll) in iteritems_(collections):
              fn = get_write_collection_path(mb_cls,
                                             self.__content_type,
                                             directory=directory)
              with open_text(os.path.join(directory, fn)) as strm:
                  dump_resource(coll, strm, content_type=self.__content_type)
docs: Dumps the given resource and all resources linked to it into a set of
          representation files in the given directory.