Add a note in Map

src/sentry/analytics/map.py

@@ -27,6 +27,8 @@ def extract(self, value: dict[str, Any] | Any | None) -> Mapping[str, Any] | Non
         if isinstance(value, dict):
             # Ensure we don't mutate the original. We do not need to deepcopy;
             # if it recurses into another Map it will once again copy itself.
+            # TODO(mgaeta): If the dictionary has a list or some other complex
+            #  object in it, that object will not be copied.
             items = value.copy()
         else:
             new_value = {}