code: def union(self, other_streamlet):
      
      from heronpy.streamlet.impl.unionbolt import UnionStreamlet
      union_streamlet = UnionStreamlet(self, other_streamlet)
      self._add_child(union_streamlet)
      other_streamlet._add_child(union_streamlet)
      return union_streamlet
docs: Returns a new Streamlet that consists of elements of both this and other_streamlet