code: def subset(self, service=None):
          
          if service is None:
              for serviceName in self.ncssServiceNames:
                  if serviceName in self.access_urls:
                      service = serviceName
                      break
              else:
                  raise RuntimeError('Subset access is not available for this dataset.')
          elif service not in self.ncssServiceNames:
              raise ValueError(service + ' is not a valid service for subset. Options are: '
                               + ', '.join(self.ncssServiceNames))
  
          return self.access_with_service(service)
docs: Subset the dataset.
  
          Open the remote dataset and get a client for talking to ``service``.
  
          Parameters
          ----------
          service : str, optional
              The name of the service for subsetting the dataset. Defaults to 'NetcdfSubset'
              or 'NetcdfServer', in that order, depending on the services listed in the
              catalog.
  
          Returns
          -------
          a client for communicating using ``service``