Update for_helpers.py

Author: BobTheBuidler

mypyc/irbuild/for_helpers.py

@@ -1213,7 +1213,7 @@ def get_expr_length(expr: Expression) -> int | None:
     # TODO: extend this, passing length of listcomp and genexp should have worthwhile
     # performance boost and can be (sometimes) figured out pretty easily. set and dict
     # comps *can* be done as well but will need special logic to consider the possibility
-    # of key conflicts
+    # of key conflicts. Range, enumerate, zip are all simple logic.
     return None