docstr: e.g. if seq_len = 3
  return:
  0 1 1
  0 0 1
  0 0 0
docstr_tok: ["e.g",".","if","seq_len","=","3","return",":","0","1","1","0","0","1","0","0","0"]
code: def dec_self_attn_mask(self, seq_len, dtype=None):
      """
      e.g. if seq_len = 3
      return:
      0 1 1
      0 0 1
      0 0 0
      """
      if dtype is None:
          dtype = self.dtype
      mask = torch.triu(torch.ones(seq_len, seq_len), diagonal=1)
      return mask.to(self.device, dtype=dtype)
  
imports: import random
  import time
  from collections import OrderedDict
  import numpy
  import torch
label_desc: Use image node_id 22 for calling the TestDecorator obj's underlying member method code with example usage: obj.dec_self_attn_mask(seq_len, dtype) and returns: mask