code: def _set_optimizer_param(optimizer, param_group, param_name, value):
      
      if param_group == 'all':
          groups = optimizer.param_groups
      else:
          groups = [optimizer.param_groups[int(param_group)]]
  
      for group in groups:
          group[param_name] = value
docs: Set a parameter on an all or a specific parameter group of an
      optimizer instance. To select all param groups, use ``param_group='all'``.