/** get the number of Dynamical Systems present in the NSDS
     \return an unsigned int
  */
 inline unsigned int getNumberOfDS() const
 {
   return _topology->dSG(0)->size();
 }
 /** get all the dynamical systems declared in the NonSmoothDynamicalSystem.
  * \return a SP::DynamicalSystemsGraph
  */
 inline const SP::DynamicalSystemsGraph dynamicalSystems() const
 {
   return _topology->dSG(0);
 }