code: def add_element(self, e):
          r
          if not isinstance(e, Iterable):
              raise TypeError("given element {} is not iterable in terms of "
                              "PyEMMAs coordinate pipeline.".format(e))
  
          # only if we have more than one element
          if not e.is_reader and len(self._chain) >= 1:
              data_producer = self._chain[-1]
              # avoid calling the setter of StreamingTransformer.data_producer, since this
              # triggers a re-parametrization even on readers (where it makes not sense)
              e._data_producer = data_producer
          e.chunksize = self.chunksize
          self._chain.append(e)
docs: r""" Appends a pipeline stage.
  
          Appends the given element to the end of the current chain.