// public methods
 void TransitionPQPReader::convertTargetedExperimentToPQP(const char* filename, OpenMS::TargetedExperiment& targeted_exp)
 {
   if (targeted_exp.containsInvalidReferences())
   {
     throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
         "Your input file contains invalid references, cannot process file.");
   }
   writePQPOutput_(filename, targeted_exp);
 }