code: def GetFeatureService(self, itemId, returnURLOnly=False):
          
          admin = None
          item = None
          try:
              admin = arcrest.manageorg.Administration(securityHandler=self._securityHandler)
              if self._securityHandler.valid == False:
                  self._valid = self._securityHandler.valid
                  self._message = self._securityHandler.message
                  return None
  
              item = admin.content.getItem(itemId=itemId)
              if item.type == "Feature Service":
                  if returnURLOnly:
                      return item.url
                  else:
                      fs = arcrest.agol.FeatureService(
                         url=item.url,
                         securityHandler=self._securityHandler)
                      if fs.layers is None or len(fs.layers) == 0 :
                          fs = arcrest.ags.FeatureService(
                             url=item.url)
                      return fs
              return None
  
          except:
              line, filename, synerror = trace()
              raise common.ArcRestHelperError({
                          "function": "GetFeatureService",
                          "line": line,
                          "filename":  filename,
                          "synerror": synerror,
                                          }
                                          )
          finally:
              admin = None
              item = None
              del item
              del admin
              gc.collect()
docs: Obtains a feature service by item ID.
  
          Args:
              itemId (str): The feature service's item ID.
              returnURLOnly (bool): A boolean value to return the URL of the feature service. Defaults to ``False``.
          Returns:
              When ``returnURLOnly`` is ``True``, the URL of the feature service is returned.
  
              When ``False``, the result from :py:func:`arcrest.agol.services.FeatureService` or :py:func:`arcrest.ags.services.FeatureService`.