adding doc comments, making Dimension Properties static

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

 
 namespace Unity.MLAgents.Sensors
 {
+    /// <summary>
+    /// A Sensor that allows to observe a variable number of entities.
+    /// </summary>
     public class BufferSensor : ISensor, IDimensionPropertiesSensor, IBuiltInSensor
     {
         private int m_MaxNumObs;
+        static DimensionProperty[] m_DimensionProperties = new DimensionProperty[]{
+                DimensionProperty.VariableSize,
+                DimensionProperty.None
+            };
         public BufferSensor(int maxNumberObs, int obsSize)
         {
             m_MaxNumObs = maxNumberObs;
         /// <inheritdoc/>
         public DimensionProperty[] GetDimensionProperties()
         {
-            return new DimensionProperty[]{
-                DimensionProperty.VariableSize,
-                DimensionProperty.None
-            };
+            return m_DimensionProperties;
         }
 
         /// <summary>
         /// <param name="obs"> The float array observation</param>
         public void AppendObservation(float[] obs)
         {
+            if (obs.Length != m_ObsSize)
+            {
+                throw new UnityAgentsException(
+                    "The BufferSensor was expecting an observation of size " +
+                    $"{m_ObsSize} but received {obs.Length} observations instead."
+                )
+            }
             if (m_CurrentNumObservables >= m_MaxNumObs)
             {
                 return;

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

 {
 
     /// <summary>
-    /// A component for BufferSensor.
+    /// A SensorComponent that creates a <see cref="BufferSensor"/>.
+        /// <summary>
+        /// This is how many floats each entities will be represented with. This number
+        /// is fixed and all entities must have the same representation.
+        /// </summary>
+
+        /// <summary>
+        /// This is the maximum number of entities the `BufferSensor` will be able to
+        /// collect.
+        /// </summary>
+
         private BufferSensor m_Sensor;
 
         /// <inheritdoc/>

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

         string m_Name;
         int[] m_Shape;
         SensorCompressionType m_CompressionType;
+        static DimensionProperty[] m_DimensionProperties = new DimensionProperty[] {
+            DimensionProperty.TranslationalEquivariance,
+            DimensionProperty.TranslationalEquivariance,
+            DimensionProperty.None };
 
         /// <summary>
         /// The Camera used for rendering the sensor observations.
         /// <returns></returns>
         public DimensionProperty[] GetDimensionProperties()
         {
-            return new DimensionProperty[] { DimensionProperty.TranslationalEquivariance, DimensionProperty.TranslationalEquivariance, DimensionProperty.None };
+            return m_DimensionProperties;
         }
 
         /// <summary>