code: def train(self, mode: bool = True) -> Attention:
      super().train(mode)
      self.ab = (
          None
          if (mode and self.ab is not None)
          else self.attention_biases[:, self.attention_bias_idxs]
      )
      return self
  
imports: from __future__ import annotations
  import itertools
  import warnings
  from typing import Any, Optional
  import torch
  import torch.nn.functional
  from torch import nn
  from torch.utils import checkpoint
  from kornia.contrib.models.common import DropPath, LayerNorm2d, window_partition, window_unpartition
  from kornia.core import Module, Tensor
  from kornia.core.check import KORNIA_CHECK
label_desc: Use image node_id 3 for calling the Attention obj's underlying member method code with example usage: obj.train(mode) and returns: self