code: def mask(self):
      return self._mask
  
imports: import math
  import numpy
  from typing import Optional
  import torch
  import torch.nn
  from neuralforecast.common._modules import TransEncoderLayer, TransEncoder, TransDecoderLayer, TransDecoder, DataEmbedding, AttentionLayer
  from ..common._base_windows import BaseWindows
  from ..losses.pytorch import MAE
label_desc: Use image node_id 2 for calling the ProbMask obj's underlying member method code with example usage: obj.mask() and returns: self