class_docstr: BERT cross attention layer.
  Based on: BERT (pytorch-transformer)
  https://github.com/huggingface/transformers
code: def forward(self, x, y):
      output_x = self.att_x(x, y)
      output_y = self.att_y(y, x)
      return self.output_x(output_x, x), self.output_y(output_y, y)
  
imports: from __future__ import annotations
  import math
  from collections.abc import Sequence
  import torch
  from torch import nn
  from monai.config.type_definitions import PathLike
  from monai.utils import optional_import
label_desc: Use image node_id 2 for calling the BertMixedLayer obj's underlying member method code with example usage: obj.forward(x, y) and returns: self,  self