public default void writeVertices(final OutputStream outputStream,final Iterator<Vertex> vertexIterator) throws IOException {
  while (vertexIterator.hasNext()) {
    writeVertex(outputStream,vertexIterator.next());
  }
}

public default void writeVertices ( final OutputStream outputStream , final Iterator < Vertex > vertexIterator ) throws IOException { while ( vertexIterator . hasNext ( ) ) { writeVertex ( outputStream , vertexIterator . next ( ) ) ; } }
write a vertex to a stream without writing its edges .
