docs: async def expand(self, request: Request, layer: BaseLayer):
          """
          Expand a layer into a list of layers including the pauses.
          """
  
          if isinstance(layer, lyr.RawText):
              t = self.reading_time(layer.text)
              yield layer
              yield lyr.Sleep(t)
  
          elif isinstance(layer, lyr.MultiText):
              texts = await render(layer.text, request, True)
  
              for text in texts:
                  t = self.reading_time(text)
                  yield lyr.RawText(text)
                  yield lyr.Sleep(t)
  
          elif isinstance(layer, lyr.Text):
              text = await render(layer.text, request)
              t = self.reading_time(text)
              yield lyr.RawText(text)
              yield lyr.Sleep(t)
  
          else:
              yield layer