code: @Override
      public FieldVisitor visitField(int access, String name, String desc, String signature, Object value) {
          fieldAlreadyExists |= name.equals(versionFieldName);
  
          return super.visitField(access, name, desc, signature, value);
      }
docs: Field visitor that observes existing fields before chaining to the
  delegate {@ClassVisitor}.
  <p> {@inheritDoc}