### Question:
Graph implements ExecutionEnvironment, AutoCloseable { public Iterator<Operation> operations() { return new OperationIterator(this); } Graph();   Graph(TF_Graph nativeHandle);   Graph(TF_Graph nativeHandle, SaverDef saverDef); @Override void close(); GraphOperation operation(String name); Iterator<Operation> operations(); @Override GraphOperationBuilder opBuilder(String type, String name); @Override Types environmentType(); void importGraphDef(GraphDef graphDef); void importGraphDef(GraphDef graphDef, String prefix); GraphDef toGraphDef(); synchronized void addInitializer(Op initializer); List<Op> initializers(); Output<?>[] addGradients(String prefix, Output<?>[] y, Output<?>[] x, Output<?>[] dx); Output<?>[] addGradients(Output<?> y, Output<?>[] x); Output<?>[] whileLoop(
      Output<?>[] inputs,
      WhileSubgraphBuilder cgBuilder,
      WhileSubgraphBuilder bgBuilder,
      String name);  }### Answer:
@Test public void iterateOverOperations() { try (Graph g = new Graph()) { Ops tf = Ops.create(g); Iterator<Operation> iterator = g.operations(); HashSet<Operation> operations; assertFalse(iterator.hasNext()); operations = new HashSet<>(); operations.add(tf.withName("Const-A").constant(1.0f).op()); operations.add(tf.withName("Const-B").constant(23).op()); operations.add(tf.withName("Const-C").constant(1.618).op()); iterator = g.operations(); assertTrue(iterator.hasNext()); assertTrue(operations.remove(iterator.next())); assertTrue(iterator.hasNext()); assertTrue(operations.remove(iterator.next())); assertTrue(iterator.hasNext()); assertTrue(operations.remove(iterator.next())); assertFalse(iterator.hasNext()); } }