code: public static <K, EV> Graph<K, NullValue, EV> fromDataSet(
  			DataSet<Edge<K, EV>> edges, ExecutionEnvironment context) {
  
  		DataSet<Vertex<K, NullValue>> vertices = edges
  			.flatMap(new EmitSrcAndTarget<>())
  				.name("Source and target IDs")
  			.distinct()
  				.name("IDs");
  
  		return new Graph<>(vertices, edges, context);
  	}
docs: Creates a graph from a DataSet of edges.
  Vertices are created automatically and their values are set to
  NullValue.
  
  @param edges a DataSet of edges.
  @param context the flink execution environment.
  @return the newly created graph.