addressed PR feedback

com.unity.perception/CHANGELOG.md

 
 The PerceptionScenario abstract class has been added to abstract perception data capture specific functionality from the vanilla scenario lifecycle. 
 
+The newly added LabelManager class now enables custom Labelers to access the list of registered Labeling Components present in the scene
+
 ### Changed
 
 Renamed all appearances of the term `KeyPoint` within types and names to `Keypoint`.

com.unity.perception/Runtime/GroundTruth/Labeling/LabelManager.cs

     /// <summary>
     /// Manages the registration of <see cref="Labeling"/> components
     /// </summary>
+    [DefaultExecutionOrder(1)]
     public class LabelManager
     {
         /// <summary>
 
         const uint k_StartingIndex = 1;
-        uint m_CurrentObjectIndex = k_StartingIndex;
+        uint m_NextObjectIndex = k_StartingIndex;
         List<IGroundTruthGenerator> m_ActiveGenerators = new List<IGroundTruthGenerator>();
         LinkedHashSet<Labeling> m_LabelsPendingRegistration = new LinkedHashSet<Labeling>();
         LinkedHashSet<Labeling> m_RegisteredLabels = new LinkedHashSet<Labeling>();
         public void RegisterPendingLabels()
         {
             if (m_RegisteredLabels.Count == 0)
-                m_CurrentObjectIndex = k_StartingIndex;
+                m_NextObjectIndex = k_StartingIndex;
 
             foreach (var unregisteredLabel in m_LabelsPendingRegistration)
             {
-                var instanceId = m_CurrentObjectIndex++;
+                var instanceId = m_NextObjectIndex++;
 
                 RecursivelyInitializeGameObjects(
                     unregisteredLabel.gameObject,
         /// Registers a labeling component
         /// </summary>
         /// <param name="labeledObject">the component to register</param>
-        public void Register(Labeling labeledObject)
+        internal void Register(Labeling labeledObject)
         {
             m_LabelsPendingRegistration.Add(labeledObject);
         }
         /// </summary>
         /// <param name="labeledObject">the component to unregister</param>
-        public void Unregister(Labeling labeledObject)
+        internal void Unregister(Labeling labeledObject)
         {
             m_LabelsPendingRegistration.Remove(labeledObject);
             m_RegisteredLabels.Remove(labeledObject);
         /// list of labels changes or when renderers or materials change on objects in the hierarchy.
         /// </summary>
         /// <param name="labeledObject">the component to refresh</param>
-        public void RefreshLabeling(Labeling labeledObject)
+        internal void RefreshLabeling(Labeling labeledObject)
         {
             m_RegisteredLabels.Remove(labeledObject);
             m_LabelsPendingRegistration.Add(labeledObject);

com.unity.perception/Tests/Runtime/GroundTruthTests/SegmentationGroundTruthTests.cs

                 if (frameStart == null || frameStart > frameCount) return;
 
                 timesSegmentationImageReceived++;
-                for (var i = 0; i < data.Length; i++)
-                    Assert.AreEqual(expectedPixelValue, data[i]);
+                CollectionAssert.AreEqual(Enumerable.Repeat(expectedPixelValue, data.Length), data.ToArray());
             }
 
             switch (segmentationKind)
             void OnSegmentationImageReceived(NativeArray<Color32> data)
             {
                 timesSegmentationImageReceived++;
-                for (var i = 0; i < data.Length; i++)
-                    Assert.AreEqual(expectedPixelValue, data[i]);
+                CollectionAssert.AreEqual(Enumerable.Repeat(expectedPixelValue, data.Length), data.ToArray());
             }
 
             var cameraObject = SetupCameraSemanticSegmentation(a => OnSegmentationImageReceived(a.data), false);
             void OnSegmentationImageReceived(NativeArray<Color32> data)
             {
                 timesSegmentationImageReceived++;
-                for (var i = 0; i < data.Length; i++)
-                    Assert.AreEqual(expectedPixelValue, data[i]);
+                CollectionAssert.AreEqual(Enumerable.Repeat(expectedPixelValue, data.Length), data.ToArray());
             }
 
             var cameraObject = SetupCameraSemanticSegmentation(a => OnSegmentationImageReceived(a.data), showVisualizations);
 
                 try
                 {
-                    for (var i = 0; i < data.Length; i++)
-                        Assert.AreEqual(expectedLabelAtFrame[frameCount], data[i]);
+                    CollectionAssert.AreEqual(Enumerable.Repeat(expectedLabelAtFrame[frameCount], data.Length), data.ToArray());
                 }
 
                 // ReSharper disable once RedundantCatchClause