code: def selected_model(self, selected_model):
      if selected_model in self.reader_pool:
          self._selected_model = selected_model
      else:
          if len(self.reader_pool) > 0:
              default_model = next(iter(self.reader_pool))
              logger.info(
                  ">> Model you are attempting to use %s does not exist in model pool. Using the following default model instead %s ",
                  selected_model,
                  default_model,
              )
              self._selected_model = default_model
          else:
              logger.info(
                  ">> No reader has been specified in config.yaml."
              )
              self._selected_model = None
  
imports: from neuralqa.reader import BERTReader
  import logging
label_desc: Use image node_id 4 for calling the ReaderPool obj's underlying member method code with example usage: obj.selected_model(selected_model) without return types