code: def mix_key(self, input_key_material: bytes):
          
          # Sets ck, temp_k = HKDF(ck, input_key_material, 2).
          self.ck, temp_k = self.noise_protocol.hkdf(self.ck, input_key_material, 2)
          # If HASHLEN is 64, then truncates temp_k to 32 bytes.
          if self.noise_protocol.hash_fn.hashlen == 64:
              temp_k = temp_k[:32]
  
          # Calls InitializeKey(temp_k).
          self.cipher_state.initialize_key(temp_k)
docs: :param input_key_material: 
          :return: