fix: check allowed file extensions in rag transform pipeline and use set type instead of list for performance in file extensions (#26593)

api/libs/collection_utils.py

@@ -0,0 +1,14 @@
+def convert_to_lower_and_upper_set(inputs: list[str] | set[str]) -> set[str]:
+    """
+    Convert a list or set of strings to a set containing both lower and upper case versions of each string.
+
+    Args:
+        inputs (list[str] | set[str]): A list or set of strings to be converted.
+
+    Returns:
+        set[str]: A set containing both lower and upper case versions of each string.
+    """
+    if not inputs:
+        return set()
+    else:
+        return {case for s in inputs if s for case in (s.lower(), s.upper())}