Okay. Let me test-drive this on the following since it has two networks present in the subclassed model SimSiam:

  
      

      keras.io
  

  
    

Keras documentation: Self-supervised contrastive learning with SimSiam 3



  

  
    
    
  

  


But I think it should be ambiguous for the callback to determine which network (out of the two) it should serialize, though.