class_docstr: weakref.ref object for tensors, np.ndarray, and structures.
  
  Invokes the callback when any element of the struct's ref-count drops to 0.
class_docstr_tok: ["weakref.ref","object","for","tensors",",","np.ndarray",",","and","structures",".","Invokes","the","callback","when","any","element","of","the","struct","'s","ref-count","drops","to","0","."]
docstr: Returns the subkey associated with the struct.
docstr_tok: ["Returns","the","subkey","associated","with","the","struct","."]
code: def subkey(self):
      """Returns the subkey associated with the struct."""
      # Potentially unsafe to return mutable subkey! If this is ever exposed
      # outside of `cache_util`, consider returning a copy.
      return self._subkey
  
imports: import collections
  import weakref
  import numpy
  import tensorflow.compat.v2
  from tensorflow.python.util import nest
label_desc: Use image node_id 6 for calling the WeakStructRef obj's underlying member method code with example usage: obj.subkey() and returns: self