code: def exists(self, folderName, serviceName=None, serviceType=None):
          
  
          url = self._url + "/exists"
          params = {
              "f" : "json",
              "folderName" : folderName,
              "serviceName" : serviceName,
              "type" : serviceType
          }
          return self._post(url=url,
                               param_dict=params,
                               securityHandler=self._securityHandler,
                               proxy_url=self._proxy_url,
                               proxy_port=self._proxy_port)
docs: This operation allows you to check whether a folder or a service
          exists. To test if a folder exists, supply only a folderName. To
          test if a service exists in a root folder, supply both serviceName
          and serviceType with folderName=None. To test if a service exists
          in a folder, supply all three parameters.
  
          Inputs:
             folderName - a folder name
             serviceName - a service name
             serviceType - a service type. Allowed values:
                  "GPSERVER", "GLOBESERVER", "MAPSERVER",
                  "GEOMETRYSERVER", "IMAGESERVER", "SEARCHSERVER",
                  "GEODATASERVER", "GEOCODESERVER"