code: def transform(self, transform_operator):
      
      from heronpy.streamlet.impl.transformbolt import TransformStreamlet
      transform_streamlet = TransformStreamlet(transform_operator, self)
      self._add_child(transform_streamlet)
      return transform_streamlet
docs: Returns a  new Streamlet by applying the transform_operator on each element of this
      streamlet. The transform_function is of the type TransformOperator.
      Before starting to cycle over the Streamlet, the open function of the transform_operator is
      called. This allows the transform_operator to do any kind of initialization/loading, etc.