@Override
 public void compute() {
   if (!kernel.getGeoGebraCAS().getCurrentCAS().isLoaded()) {
     inputFingerprint = null;
     return;
   }
   String inputFingerprintPrev = inputFingerprint;
   setInputOutput();
   if (inputFingerprintPrev == null || !inputFingerprintPrev.equals(inputFingerprint)) {
     Log.trace(inputFingerprintPrev + " -> " + inputFingerprint);
     initialCompute();
   }
 }