code: def _track_class(cls, fields):
      
      # Small tests to ensure everything is all right
      assert not getattr(cls, '_is_tracked', False)
  
      for field in fields:
          _track_class_field(cls, field)
  
      _add_signals_to_cls(cls)
  
      # Mark the class as tracked
      cls._is_tracked = True
      # Do not directly track related fields (tracked on related model)
      # or m2m fields (tracked by another signal)
      cls._tracked_fields = [
          field for field in fields
          if '__' not in field
      ]
docs: Track fields on the specified model