fix mypy err

Author: BobTheBuidler

mypyc/irbuild/specialize.py

@@ -570,7 +570,7 @@ def body_insts() -> None:
 
         index_type = builder._analyze_iterable_item_type(arg)
         index = _create_iterable_lexpr(index_name, index_type)
-        index_reg = builder.add_local_reg(index.node, builder.type_to_rtype(index_type))
+        index_reg = builder.add_local_reg(index.node, builder.type_to_rtype(index_type))  # type: ignore [arg-type]
 
         for_loop_helper(builder, index, arg, body_insts, None, is_async=False, line=expr.line)
         return retval