standard-tests: retriever docstrings (#28596)

libs/standard-tests/langchain_tests/base.py

@@ -10,6 +10,8 @@ class BaseStandardTests(ABC):
     def test_no_overrides_DO_NOT_OVERRIDE(self) -> None:
         """
         Test that no standard tests are overridden.
+
+        :private:
         """
         # find path to standard test implementations
         comparison_class = None