code: def copy_fields(src, to):
      
      args = tuple(getattr(src, field.attname) for field in src._meta.fields)
      return to(*args)
docs: Returns a new instance of `to_cls` with fields data fetched from `src`.
      Useful for getting a model proxy instance from concrete model instance or
      the other way around. Note that we use *arg calling to get a faster model
      initialization.