code: @Override
      @InterfaceAudience.Public
      public Map<String, Object> getProperties() {
          Map<String, Object> properties = revisionInternal.getProperties();
          if (!checkedProperties) {
              if (properties == null) {
                  if (loadProperties() == true) {
                      properties = revisionInternal.getProperties();
                  }
              }
              checkedProperties = true;
          }
          return properties != null ? Collections.unmodifiableMap(properties) : null;
      }
docs: The contents of this revision of the document.
  Any keys in the dictionary that begin with "_", such as "_id" and "_rev", contain
  CouchbaseLite metadata.
  
  @return contents of this revision of the document.