code: def pick(self, *props):
          
          result = Parameters()
          for prop in props:
              if self.contains_key(prop):
                  result.put(prop, self.get(prop))
          return result
docs: Picks select parameters from this Parameters and returns them as a new Parameters object.
  
          :param props: keys to be picked and copied over to new Parameters.
  
          :return: a new Parameters object.