def register_handler(queues, opts={}, handler=nil, &block) #:nodoc:
      Array(queues).each do |queue|
        @handlers[queue] = [opts.symbolize_keys, handler || block]
      end
    end
def register_handler(queues, opts={}, handler=nil, &block) #:nodoc:
      Array(queues).each do |queue|
        @handlers[queue] = [opts.symbolize_keys, handler || block]
      end
    end
register handler for the given queues (see Client#register_handler)