code: public Version getBaseVersion() throws UnsupportedRepositoryOperationException, RepositoryException
     {
        checkValid();
  
        if (!this.isNodeType(Constants.MIX_VERSIONABLE))
        {
           throw new UnsupportedRepositoryOperationException("Node is not versionable " + getPath());
        }
  
        PropertyData bvProp =
           (PropertyData)dataManager.getItemData(nodeData(), new QPathEntry(Constants.JCR_BASEVERSION, 1),
              ItemType.PROPERTY);
  
        return (Version)dataManager.getItemByIdentifier(ValueDataUtil.getString(bvProp.getValues().get(0)), true, false);
     }
docs: {@inheritDoc}