code: def build_attention_mask(self):
      mask = paddle.empty(
          shape=[self.context_length, self.context_length]
      )
      mask.fill_(value=float("-inf"))
      mask = paddle.tensor.triu(mask, diagonal=1)
      return mask
  
imports: from collections import OrderedDict
  from typing import Tuple, Union
  import numpy
  import paddle
  from paddle.nn.initializer import Constant
  from paddle.vision.transforms import Compose, Resize, CenterCrop, ToTensor, Normalize
label_desc: Use image node_id 2 for calling the CLIP obj's underlying member method code with example usage: obj.build_attention_mask() and returns: mask