docs: def get_layers(self, class_: Type[L], became: bool=True) -> List[L]:
          """
          Returns the list of layers of a given class. If no layers are present
          then the list will be empty.
  
          :param class_: class of the expected layers
          :param became: Allow transformed layers in results
          """
  
          out = self._index.get(class_, [])
  
          if became:
              out += self._transformed.get(class_, [])
  
          return out