def get(id)
      @brokers.each { |b| return b.identity if b.identity == id || b.alias == id }
      nil
    end
def get(id)
      @brokers.each { |b| return b.identity if b.identity == id || b.alias == id }
      nil
    end
Get broker serialized identity if client exists

 === Parameters
 id(Integer|String):: Broker alias or serialized identity

 === Return
 (String|nil):: Broker serialized identity if client found, otherwise nil