code: private void parseFieldRemove(String fieldName, UNode addNode) {
          Set<String> removeValueSet = new LinkedHashSet<>();
          for (UNode valueNode : addNode.getMemberList()) {
              Utils.require(valueNode.isValue() && valueNode.getName().equals("value"),
                            "Value expected for 'remove' element: " + valueNode);
              removeValueSet.add(valueNode.getValue());
          }
          removeFieldValues(fieldName, removeValueSet);
      }
docs: Parse an "add" update to a field.