[TransitionPlanner] Add comment.

Author: florent-lamiraux

include/hpp/manipulation/path-planner/transition-planner.hh

@@ -145,6 +145,9 @@ class HPP_MANIPULATION_DLLAPI TransitionPlanner : public core::PathPlanner {
   void clearPathOptimizers();
 
   /// Add a path optimizer
+  ///
+  /// \note The input path optimizer should have been constructed with the inner problem of this
+  /// class.
   void addPathOptimizer(const PathOptimizerPtr_t& pathOptimizer);
 
   /// Set parameter to the inner problem