Address comments

com.unity.ml-agents/Runtime/Communicator/GrpcExtensions.cs

             observationProto.Shape.AddRange(shape);
 
             var typeSensor = sensor as ITypedSensor;
-            observationProto.SensorType = (SensorTypeProto)typeSensor.GetSensorType();
+            if (typeSensor != null)
+            {
+                observationProto.SensorType = (SensorTypeProto)typeSensor.GetSensorType();
+            }
+            else
+            {
+                observationProto.SensorType = SensorTypeProto.Observation;
+            }
             return observationProto;
         }
 

com.unity.ml-agents/Runtime/Sensors/ITypedSensor.cs

 {
 
     /// <summary>
-    /// The SensorType flag of the observation
+    /// The SensorType enum of the observation
-    [System.Flags]
-    public enum SensorType
+    internal enum SensorType
     {
         Observation = 0,
         Goal = 1,
     /// <summary>
     /// Sensor interface for sensors with variable types.
     /// </summary>
-    public interface ITypedSensor
+    internal interface ITypedSensor
     {
         /// <summary>
         /// Returns the SensorType enum corresponding to the type of the sensor.

com.unity.ml-agents/Runtime/Sensors/VectorSensor.cs

     /// <summary>
     /// A sensor implementation for vector observations.
     /// </summary>
-    public class VectorSensor : ISensor, ITypedSensor
+    public class VectorSensor : ISensor
     {
         // TODO use float[] instead
         // TODO allow setting float[]
-        SensorType m_sensorType;
 
         /// <summary>
         /// Initializes the sensor.
 
             m_Observations = new List<float>(observationSize);
             m_Name = name;
-            m_sensorType = SensorType.Observation;
             m_Shape = new[] { observationSize };
         }
 
         public int[] GetObservationShape()
         {
             return m_Shape;
-        }
-
-        public SensorType GetSensorType()
-        {
-            return m_sensorType;
         }
 
         /// <inheritdoc/>

ml-agents-envs/mlagents_envs/rpc_utils.py

     :param agent_info: protobuf object.
     :return: BehaviorSpec object.
     """
-    observation_shape = [tuple(obs.shape) for obs in agent_info.observations]
-    dim_props = [
-        tuple(DimensionProperty(dim) for dim in obs.dimension_properties)
-        for obs in agent_info.observations
-    ]
-    sensor_types = [SensorType(obs.sensor_type) for obs in agent_info.observations]
-    sensor_specs = [
-        SensorSpec(obs_shape, dim_p, sensor_type)
-        for obs_shape, dim_p, sensor_type in zip(
-            observation_shape, dim_props, sensor_types
+    sensor_specs = []
+    for obs in agent_info.observations:
+        sensor_specs.append(
+            SensorSpec(
+                tuple(obs.shape),
+                tuple(DimensionProperty(dim) for dim in obs.dimension_properties),
+                SensorType(obs.sensor_type),
+            )
-    ]
     # proto from communicator < v1.3 does not set action spec, use deprecated fields instead
     if (
         brain_param_proto.action_spec.num_continuous_actions == 0