Documentation example of customising model instance loading has a bug

[Ali Toosi]

The docs provide an example of how the model instance loading can be changed and how _loaded_values can be saved for future comparison here: ​https://docs.djangoproject.com/en/4.0/ref/models/instances/

In this example, it checks if there are any values not loaded from db then add them as DEFERRED values so class instantiation would work (cls(*values)). However, this would mean values list has items now that do not map to any field_names so when at the end of the function, we zip them together and store in _loaded_values, the code will fail.

The easiest fix for this is to update the field_names too so they would 1. work and 2. show which fields were not loaded from the db at the time.