Fix to test for codegen naming + addition of python codegen dict

Author: talvandaalen

servicex/config_default.yaml

@@ -38,3 +38,6 @@ backend_types:
   - type: cms_run1_aod
     return_data: root-file
     codegen: cms
+  - type: python
+    return_data: parquet
+    codegen: python

tests/test_servicex.py

@@ -1368,7 +1368,7 @@ async def test_codegen_default_by_backend(mocker, good_awkward_file_data):
     await ds.get_data_rootfiles_async("(valid qastle string)")
 
     called = mock_servicex_adaptor.query_json
-    assert called["codegen"] == "xaod_r21"
+    assert called["codegen"] == "atlasxaod"
 
 
 @pytest.mark.asyncio