code: def visibility_mask_to_attention_bias(visible, dtype):
      """Convert a boolean visibility mask to an attention bias.
  
      The returned Tensor has large negative values in positions where
      visible=False.
  
      Args:
        visible: a boolean Tensor
        dtype: a dtype
      Returns:
        a Tensor with the given dtype and the same shape as "visible"
      """
      return mtf.cast(mtf.logical_not(visible), dtype) * -1e9
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import mesh_tensorflow
  import tensorflow.compat.v1
label_desc: Use image node_id 7 for calling a global function with example usage: visibility_mask_to_attention_bias(visible, dtype) and returns: unknown