code: def get(self, subset=None):
          
          if subset is None:
              return dict((name, attr.get(copy=True)) for name, attr in self._fields.items())
          else:
              return dict((name, attr.get(copy=True)) for name, attr in self._fields.items() if name in subset)
docs: Return a dictionary object with the registered fields and their values
  
             Optional rgument:
              | ``subset``  --  a list of names to restrict the number of fields
                                in the result