def fetch(*queues)
      job = nil
      transaction do
        command("FETCH", *queues)
        job = result!
      end
      JSON.parse(job) if job
    end
def fetch(*queues)
      job = nil
      transaction do
        command("FETCH", *queues)
        job = result!
      end
      JSON.parse(job) if job
    end
Returns either a job hash or falsy.