class_docstr: ## Updated Feedback Transformer Module
  
  This is the updated feedback transformer module that caches the keys and values.
class_docstr_tok: ["#","#","Updated","Feedback","Transformer","Module","This","is","the","updated","feedback","transformer","module","that","caches","the","keys","and","values","."]
code: def free(self):
      self.mem_key.free()
      self.mem_value.free()
  
imports: import math
  from typing import Optional
  import torch
  from torch import nn
  from labml_helpers.module import Module
  from labml_nn.transformers.feed_forward import FeedForward
  from labml_nn.transformers.mha import PrepareForMultiHeadAttention
  from labml_nn.utils import clone_module_list
label_desc: Use image node_id 3 for calling the FeedbackTransformerKV obj's underlying member method code with example usage: obj.free() without return types