class_docstr: ### Stack Module
  
  This uses the stack function defined above, and does the necessary initializations.
class_docstr_tok: ["#","#","#","Stack","Module","This","uses","the","stack","function","defined","above",",","and","does","the","necessary","initializations","."]
docstr: To release memory
docstr_tok: ["To","release","memory"]
code: def free(self):
      """
      To release memory
      """
  
      self.memory = None
      self.memory_grad = None
      self.last = None
  
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 4 for calling the Stack obj's underlying member method code with example usage: obj.free() without return types