fixed scenario UI for configuration asset

com.unity.perception/Editor/Randomization/Editors/ScenarioBaseEditor.cs

                         m_HasConstantsField = true;
                         UIElementsEditorUtilities.CreatePropertyFields(iterator.Copy(), m_ConstantsListVisualContainer);
                         break;
+                    case "configuration":
+                        break;
                     default:
                     {
                         foundProperties = true;

com.unity.perception/Editor/Randomization/Uxml/ScenarioBaseElement.uxml

                 class="scenario__info-box"
                 text="Scenarios control the execution flow of your simulation by applying randomization parameters. Make sure to always have only one scenario active within your scene."/>
             <VisualElement name="constants-container">
+                <editor:PropertyField
+                    name="configuration-asset"
+                    label="Configuration"
+                    binding-path="configuration"
+                    style="margin-left: 13 px;"
+                    tooltip="References a JSON configuration text asset to load at runtime before the scenario starts executing. Scenario configuration files can be created using the Generate JSON Config button below."/>
-                <editor:PropertyField name="configuration-file-name" label="Constants File Name" binding-path="serializedConstantsFileName"/>
                 <VisualElement style="flex-direction: row;">
                     <Button name="generate-json-config" text="Generate JSON Config" style="flex-grow: 1;"
                         tooltip="Serializes scenario constants and randomizer settings to a JSON configuration file"/>

com.unity.perception/Runtime/Randomization/Randomizers/AssetSources/AssetSource.cs

         [SerializeReference] public AssetSourceLocation assetSourceLocation = new LocalAssetSourceLocation();
 
         bool m_Initialized;
-        UniformSampler m_Sampler = new UniformSampler();
 
         /// <summary>
         /// The archetype used to preprocess assets from this source
         public int Count => assetSourceLocation.Count;
 
         /// <summary>
-        /// Execute setup steps for this AssetSource
+        /// Execute setup steps for this AssetSource. It is often unnecessary to call this API directly since all other
+        /// relevant APIs in this class will Initialize() this AssetSource if it hasn't been already.
-            assetSourceLocation.Initialize(archetype);
-            m_Initialized = true;
+            if (!m_Initialized)
+            {
+                assetSourceLocation.Initialize(archetype);
+                m_Initialized = true;
+            }
         }
 
         /// <summary>
         public T LoadRawAsset(int index)
         {
             CheckIfInitialized();
+            if (Count == 0)
+                return null;
             return assetSourceLocation.LoadAsset<T>(index);
         }
 
         /// <returns>All assets that can be loaded from this AssetSource</returns>
         public T[] LoadAllRawAssets()
         {
+            CheckIfInitialized();
             var array = new T[Count];
             for (var i = 0; i < Count; i++)
                 array[i] = LoadRawAsset(i);
         /// <returns>Instantiated instances from every loadable asset</returns>
         public T[] CreateProcessedInstances()
         {
+            CheckIfInitialized();
-        }
-
-        /// <summary>
-        /// Returns a uniformly random sampled asset from this AssetSource
-        /// </summary>
-        /// <returns>The randomly sampled asset</returns>
-        public T SampleAsset()
-        {
-            CheckIfInitialized();
-            if (Count == 0)
-                return null;
-
-            return assetSourceLocation.LoadAsset<T>((int)(m_Sampler.Sample() * Count));
-        }
-
-        /// <summary>
-        /// Instantiates and preprocesses a uniformly random sampled asset from this AssetSource
-        /// </summary>
-        /// <returns>The generated random instance</returns>
-        public T SampleInstance()
-        {
-            CheckIfInitialized();
-            return CreateProcessedInstance(SampleAsset());
         }
 
         /// <summary>

com.unity.perception/Runtime/Randomization/Scenarios/ScenarioBase.cs

         /// <summary>
         /// The list of randomizers managed by this scenario
         /// </summary>
-        [HideInInspector, SerializeReference] List<Randomizer> m_Randomizers = new List<Randomizer>();
+        [SerializeReference] List<Randomizer> m_Randomizers = new List<Randomizer>();
-        [HideInInspector] public TextAsset configuration;
+        public TextAsset configuration;
 
         /// <summary>
         /// Enumerates over all enabled randomizers