Fix the comment to match the code.
Looking at the impl, it only accepts sets.
diff --git a/lib/new_sets.bzl b/lib/new_sets.bzl
index 332e9c5..cd90a30 100644
--- a/lib/new_sets.bzl
+++ b/lib/new_sets.bzl
@@ -182,10 +182,10 @@
"""Returns the union of several sets.
Args:
- *args: An arbitrary number of sets or lists.
+ *args: An arbitrary number of sets.
Returns:
- The set union of all sets or lists in `*args`.
+ The set union of all sets in `*args`.
"""
return struct(_values = dicts.add(*[s._values for s in args]))
