code: @InterfaceAudience.Public
      public Map<String, Object> getUserProperties() {
          return getCurrentRevision() == null ? null : getCurrentRevision().getUserProperties();
      }
docs: The user-defined properties, without the ones reserved by CouchDB.
  This is based on -properties, with every key whose name starts with "_" removed.
  
  @return user-defined properties, without the ones reserved by CouchDB.