code: def __init__(self, B, L, device="cpu"):
      mask_shape = [B, 1, L, L]
      with torch.no_grad():
          self._mask = torch.triu(
              torch.ones(mask_shape, dtype=torch.bool), diagonal=1
          ).to(device)
  
imports: import os
  import math
  import numpy
  from math import sqrt
  from scipy.fftpack import next_fast_len
label_desc: Use image node_id 1 to create a new TriangularCausalMask object  with example: obj = TriangularCausalMask(B, L, device)