code: def _get_kwarg(self, name, kwargs):
          
          at_name = '@{}'.format(name)
  
          if name in kwargs:
              if at_name in kwargs:
                  raise ValueError('Both {!r} and {!r} specified in kwargs'.format(name, at_name))
              return kwargs[name]
  
          if at_name in kwargs:
              return kwargs[at_name]
  
          return not_set
docs: Helper to get value of a named attribute irrespective of whether it is passed
          with or without "@" prefix.