code: public DataSet<Tuple2<K, LongValue>> outDegrees() {
  
  		return vertices.coGroup(edges).where(0).equalTo(0).with(new CountNeighborsCoGroup<>())
  			.name("Out-degree");
  	}
docs: Return the out-degree of all vertices in the graph.
  
  @return A DataSet of {@code Tuple2<vertexId, outDegree>}