code: def http(klass, url, interval, timeout=None, deregister=None, header=None):
          
          ret = {'http': url, 'interval': interval}
          if timeout:
              ret['timeout'] = timeout
          if deregister:
              ret['DeregisterCriticalServiceAfter'] = deregister
          if header:
              ret['header'] = header
          return ret
docs: Peform a HTTP GET against *url* every *interval* (e.g. "10s") to peform
          health check with an optional *timeout* and optional *deregister* after
          which a failing service will be automatically deregistered. Optional
          parameter *header* specifies headers sent in HTTP request. *header*
          paramater is in form of map of lists of strings,
          e.g. {"x-foo": ["bar", "baz"]}.