code: def _aggregate(self):
          '''
          The function aggreagtes all pre_stream, layout and post_stream and
          components, and yields them one by one.
          '''
          # Yielding everything under pre_stream
          for x in self._yield_all(self.pre_stream): yield x
  
          # Yielding layout
          for x in self._yield_all(self.layout): yield x
  
          # Yield LayoutSR Specific Content
          yield  % (
              self.stream_div_id,
              self.stream_div_id,
              self.stream_div_layout_id
          )
  
          # Yielding components
          for x in self._yield_all(self.components): yield x
  
          # Yield LayoutSR Specific Content
          yield """</div>"""
  
          # Yielding everything under post_stream
          for x in self._yield_all(self.post_stream): yield x
docs: The function aggreagtes all pre_stream, layout and post_stream and
          components, and yields them one by one.