code: def validate(cls, job_config):
      
      if job_config.output_writer_cls != cls:
        raise errors.BadWriterParamsError(
            "Expect output writer class %r, got %r." %
            (cls, job_config.output_writer_cls))
docs: Validates relevant parameters.
  
      This method can validate fields which it deems relevant.
  
      Args:
        job_config: an instance of map_job.JobConfig.
  
      Raises:
        errors.BadWriterParamsError: required parameters are missing or invalid.