code: def __add__(self, other):
      assert self.ek == other.ek
      return add(self.ek, self, other)
  
imports: from typing import Optional
  from typing import Tuple
  import tensorflow
  import tf_big
label_desc: Use image node_id 3 for calling the Ciphertext obj's underlying member method code with example usage: obj.__add__(other) and returns: add