Add method for checking whether `SideEffect` is active

sources/BaseAPI/API/SideEffects/SideEffectAPI.uc

@@ -120,6 +120,24 @@ public function SideEffect Add_S(
     return newSideEffect;
 }
 
+/// Checks whether specified [`SideEffect`] is currently active.
+///
+/// Check is done via contents and not instance equality.
+/// Returns `true` if specified [`SideEffect`] is currently active and `false` otherwise.
+public function bool IsRegistered(SideEffect sideEffectToCheck) {
+    local int i;
+
+    if (sideEffectToCheck == none)          return false;
+    if (!sideEffectToCheck.IsInitialized()) return false;
+
+    for (i = 0; i < activeSideEffects.length; i += 1) {
+        if (activeSideEffects[i].IsEqual(sideEffectToCheck)) {
+            return true;
+        }
+    }
+    return false;
+}
+
 /// Adds a new side effect to the list of active side effects.
 ///
 /// This method will fail if its argument is `none`, non-initialized or a side effect with that