Address feedback

Author: JukkaL

mypyc/lower/list_ops.py

@@ -48,8 +48,10 @@ def list_items(builder: LowLevelIRBuilder, args: list[Value], line: int) -> Valu
 def list_item_ptr(builder: LowLevelIRBuilder, obj: Value, index: Value, line: int) -> Value:
     """Get a pointer to a list item (index must be valid and non-negative).
 
-    Type of index must be c_pyssize_t_rprimitive.
+    Type of index must be c_pyssize_t_rprimitive, and obj must refer to a list object.
     """
+    # List items are represented as an array of pointers. Pointer to the item obj[index] is
+    # <pointer to first item> + index * <pointer size>.
     items = list_items(builder, [obj], line)
     delta = builder.add(
         IntOp(