code: public boolean isForeignKeyChanged() {
          return CollectionUtils.exists(differences.values(), new Predicate() {
              @Override
              public boolean evaluate(Object object) {
                  return ((ModelDiffEntry) object).isForeignKey();
              }
          });
      }
docs: Returns true if one of the differences of this ModelDiff instance is an OpenEngSBForeignKey. Returns false
  otherwise.