Merge remote-tracking branch 'origin/refactor-isnull-op' into refactor-isnull-op

Author: tswast

bigframes/core/compile/polars/operations/__init__.py

@@ -17,5 +17,5 @@
 This directory structure should reflect the same layout as the
 `bigframes/operations` directory where the operations are defined.
 
-Prefer one file per op to keep file sizes manageable for text editors and LLMs.
+Prefer small groups of ops per file to keep file sizes manageable for text editors and LLMs.
 """