code: def build_nested_field(self, field_name, relation_info, nested_depth):
          
          if field_name != 'children':
              return super(PriceEstimateSerializer, self).build_nested_field(field_name, relation_info, nested_depth)
          field_class = self.__class__
          field_kwargs = {'read_only': True, 'many': True, 'context': {'depth': nested_depth - 1}}
          return field_class, field_kwargs
docs: Use PriceEstimateSerializer to serialize estimate children