fix: do not store stringified spectral match assignment

Author: michaelwenk

src/casekit/nmr/fragments/FragmentUtilities.java

@@ -6,16 +6,13 @@
 import casekit.nmr.model.Spectrum;
 import casekit.nmr.similarity.Similarity;
 import casekit.nmr.utils.Utils;
-import com.google.gson.Gson;
 import org.openscience.cdk.interfaces.IAtomContainer;
 
 import java.util.*;
 import java.util.stream.Collectors;
 
 public class FragmentUtilities {
 
-    private final static Gson gson = new Gson();
-
     public static LinkedHashMap<String, List<DataSet>> sortByFrequencies(
             final Map<String, List<DataSet>> functionalGroupDataSetsMap) {
         final LinkedHashMap<String, List<DataSet>> sortedCollection = new LinkedHashMap<>();
@@ -131,7 +128,7 @@ public static boolean isMatch(final DataSet dataSet, final Spectrum querySpectru
         if (!checkHybridizations(dataSet, matchAssignment, queryHybridizationList)) {
             return false;
         }
-        dataSet.addAttachment("spectralMatchAssignment", gson.toJson(matchAssignment, Assignment.class));
+        dataSet.addAttachment("spectralMatchAssignment", matchAssignment);
         final Double rmsd = Similarity.calculateRMSD(spectrum, querySpectrum, 0, 0, matchAssignment);
         dataSet.addAttachment("averageDeviation", averageDeviation);
         dataSet.addAttachment("rmsd", rmsd);