code: def get_natural_key_info(cls):
          
          fields = cls.get_natural_key_def()
          info = []
          for name in fields:
              field = cls._meta.get_field(name)
              rel_to = None
              if hasattr(field, 'rel'):
                  rel_to = field.rel.to if field.rel else None
              elif hasattr(field, 'remote_field'):
                  if field.remote_field:
                      rel_to = field.remote_field.model
                  else:
                      rel_to = None
              info.append((name, rel_to))
          return info
docs: Derive natural key from first unique_together definition, noting which
          fields are related objects vs. regular fields.