Add comments

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

             }
             observationProto.Shape.AddRange(shape);
 
+            // Add the observation type, if any, to the observationProto
             var typeSensor = sensor as ITypedSensor;
             if (typeSensor != null)
             {

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

     /// </summary>
     internal enum ObservationType
     {
+        // Collected observations are generic.
+        // Collected observations contain goal information.
+        // Collected observations contain reward information.
+        // Collected observations are messages from other agents.
         Message = 3,
     }
 

ml-agents-envs/mlagents_envs/base_env.py

 
 
 class ObservationType(Enum):
+    '''
+    An Enum which defines the type of information carried in the observation
+    of the agent.
+    '''
+    # Observation information is generic.
+    # Observation contains goal information for current task.
+    # Observation contains reward information for current task.
+    # Observation contains a message from another agent.
     MESSAGE = 3