/**
* @brief Specialized MotionIndex to control blend shape.
- * We can control the blend shape by index (when we set BlendShapeId as IndexKey)
- * or by name (when we set BlendShapeId as StringKey)
+ * We can control the blend shape by index (when we set BlendShapeId as IndexKey),
+ * or by name (when we set BlendShapeId as StringKey).
+ *
+ * MotionValue should be float type.
*
* @code
*