How to convert ODocument to OrientVertex in orientdb

Create custom class CVertex
public class CVertex extends OrientVertex{

    public CVertex(OrientBaseGraph graph, OIdentifiable record) {
        super(graph, record);
        // TODO Auto-generated constructor stub
    }
    public OrientVertex get(){
        return (OrientVertex)this;
    }

}   

OrientGraph graph = new OrientGraph(
            "dburl", "admin", "admin");

OIndexManager idxManager = graph.getRawGraph().getMetadata().getIndexManager();
        OIndex<?> idx = idxManager.getIndex(INDEX_CONSTANTS.FB_ID_INDEX);
        OIdentifiable user = (OIdentifiable) idx.get(fbId);
        if(null==user){
            return null;
        }
        final ODocument value = ((OIdentifiable) user).getRecord();
        CVertex v = null;
        if (value.getSchemaClass().isSubClassOf(OrientVertex.CLASS_NAME)) {
            // DIRECT VERTEX
            v = new CVertex(graph, value);
        }else{
            return null;
        }
        return v.get();