code: public void setProperties(Map<String, Value> properties) {
          if (properties != null) {
              this.properties = new HashMap<>(properties);
          } else {
              this.properties = null;
          }
      }
docs: Overrides the properties for copies made with this visitor.
  
  @param properties a map of property name to value pairs, or
  <code>null</code> to use the original proposition's value for this field.