code: def output(self, context, *args, **kwargs):
          
  
          output_fields = self.output_fields
          output_type = self.output_type
  
          if output_fields and output_type:
              raise UnrecoverableError("Cannot specify both output_fields and output_type option.")
  
          if self.output_type:
              context.set_output_type(self.output_type)
  
          if self.output_fields:
              context.set_output_fields(self.output_fields)
  
          yield
docs: Allow all readers to use eventually use output_fields XOR output_type options.