def process(job = nil, &block)
      return unless job ||= reserve

      job.worker = self
      working_on job
      perform(job, &block)
    ensure
      done_working
    end
def process(job = nil, &block)
      return unless job ||= reserve

      job.worker = self
      working_on job
      perform(job, &block)
    ensure
      done_working
    end
DEPRECATED. Processes a single job. If none is given, it will
 try to produce one. Usually run in the child.