Handle duplicate references args to Client.get() (#259, #260)

- Add test of #259
- Fix duplicate `references`
- Add #259, #260 to doc/whatsnew

---------

Co-authored-by: Paul Natsuo Kishimoto <[email protected]>

Author: benfrankel

doc/whatsnew.rst

@@ -14,6 +14,7 @@ Next release
   with both :py:`version=...` and :py:`urn=...` would raise :class:`ValueError`
   even if the two were in agreement.
 - Fix two regressions in :func:`.to_pandas` introduced in v2.23.0 (:issue:`251`, :pull:`252`).
+- Fix a bug where supplying `references=...` to ESTAT or EMPL would raise :class:`ValueError` (thanks :gh-user:`benfrankel` for :issue:`259`, :pull:`260`).
 
 v2.23.1 (2025-10-01)
 ====================

sdmx/source/estat.py

@@ -36,6 +36,8 @@ def handle_references_param(kwargs: dict) -> None:
         kwargs.get("resource", None), "id", None
     )
     params = kwargs.setdefault("params", {})
+    if "references" in kwargs:
+        params["references"] = kwargs.pop("references")
 
     # Preempt default values that would be set by Client._request_from_args()
     if not params.get("references"):

sdmx/tests/test_sources.py

@@ -321,6 +321,10 @@ class TestEMPL(DataSourceTest):
         "dataflow": dict(resource_id="LMP_IND_EXP"),
     }
 
+    def test_gh_259(self, client):
+        """Test of https://github.com/khaeru/sdmx/issues/259."""
+        client.dataflow("LMP_EXPME", references="children")
+
 
 class TestGROW(DataSourceTest):
     source_id = "GROW"