Make ActionSpec constructor public (#4896)

com.unity.ml-agents/CHANGELOG.md

 
 ### Minor Changes
 #### com.unity.ml-agents / com.unity.ml-agents.extensions (C#)
+- The `ActionSpec` constructor is now public. Previously, it was not possible to create an
+  ActionSpec with both continuous and discrete actions from code. (#4896)
-will result in the values being summed (instead of averaged) when written to
-TensorBoard. Thanks to @brccabral for the contribution! (#4816)
+  will result in the values being summed (instead of averaged) when written to
+  TensorBoard. Thanks to @brccabral for the contribution! (#4816)
 - The upper limit for the time scale (by setting the `--time-scale` paramater in mlagents-learn) was
 removed when training with a player. The Editor still requires it to be clamped to 100. (#4867)
 - Added the IHeuristicProvider interface to allow IActuators as well as Agent implement the Heuristic function to generate actions.

com.unity.ml-agents/Runtime/Actuators/ActionSpec.cs

         /// <summary>
         /// Creates a Continuous <see cref="ActionSpec"/> with the number of actions available.
         /// </summary>
-        /// <param name="numActions">The number of actions available.</param>
+        /// <param name="numActions">The number of continuous actions available.</param>
         /// <returns>An Continuous ActionSpec initialized with the number of actions available.</returns>
         public static ActionSpec MakeContinuous(int numActions)
         {
             return actuatorSpace;
         }
 
-        internal ActionSpec(int numContinuousActions, int[] branchSizes = null)
+        /// <summary>
+        /// Create an ActionSpec initialized with the specified action sizes.
+        /// </summary>
+        /// <param name="numContinuousActions">The number of continuous actions available.</param>
+        /// <param name="discreteBranchSizes">The array of branch sizes for the discrete actions.  Each index
+        /// contains the number of actions available for that branch.</param>
+        /// <returns>An ActionSpec initialized with the specified action sizes.</returns>
+        public ActionSpec(int numContinuousActions = 0, int[] discreteBranchSizes = null)
-            BranchSizes = branchSizes;
+            BranchSizes = discreteBranchSizes;
         }
 
         /// <summary>

com.unity.ml-agents/Tests/Runtime/RuntimeAPITest.cs

             var behaviorParams = gameObject.AddComponent<BehaviorParameters>();
             behaviorParams.BrainParameters.VectorObservationSize = 3;
             behaviorParams.BrainParameters.NumStackedVectorObservations = 2;
-            behaviorParams.BrainParameters.VectorActionDescriptions = new[] { "TestActionA", "TestActionB" };
-            behaviorParams.BrainParameters.ActionSpec = ActionSpec.MakeDiscrete(2, 2);
+            behaviorParams.BrainParameters.VectorActionDescriptions = new[] { "Continuous1", "TestActionA", "TestActionB" };
+            behaviorParams.BrainParameters.ActionSpec = new ActionSpec(1, new []{2, 2});
             behaviorParams.BehaviorName = "TestBehavior";
             behaviorParams.TeamId = 42;
             behaviorParams.UseChildSensors = true;