Add missing requireHandles

Signed-off-by: Ryan Nett <rnett@calpoly.edu>

Author: rnett

tensorflow-core/tensorflow-core-api/src/main/java/org/tensorflow/GraphOperation.java

@@ -188,13 +188,15 @@ Tensor tensor(int outputIdx) {
    * Get the number of inputs to the op, not including control inputs.
    */
   public int numInputs() {
+    requireHandle(unsafeNativeHandle);
     return TF_OperationNumInputs(getUnsafeNativeHandle());
   }
 
   /**
    * Get the op's inputs, not including control inputs.
    */
   public List<Operand<?>> inputs() {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       int numInputs = numInputs();
       TF_Output handles = new TF_Output(numInputs);
@@ -219,6 +221,7 @@ public List<Operand<?>> inputs() {
    * @param index the output to look for usages of
    */
   public int numConsumers(int index) {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       TF_Output output = new TF_Output().oper(getUnsafeNativeHandle()).index(index);
       return TF_OperationOutputNumConsumers(output);
@@ -231,6 +234,7 @@ public int numConsumers(int index) {
    * @param index the output to look for usages of
    */
   public Set<GraphOperation> consumers(int index) {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       TF_Output output = new TF_Output().oper(getUnsafeNativeHandle()).index(index);
       int numConsumers = numConsumers(index);
@@ -253,6 +257,7 @@ public Set<GraphOperation> consumers(int index) {
    * Get the number of ops that use any of this op's outputs as an input, not including control dependencies.
    */
   public int numConsumers() {
+    requireHandle(unsafeNativeHandle);
     int all = 0;
     for (int i = 0; i < numOutputs(); i++) {
       all += numConsumers(i);
@@ -265,6 +270,7 @@ public int numConsumers() {
    * Get the ops that use any of this op's outputs as an input, not including control dependencies.
    */
   public Set<GraphOperation> consumers() {
+    requireHandle(unsafeNativeHandle);
     Set<GraphOperation> all = new LinkedHashSet<>();
     for (int i = 0; i < numOutputs(); i++) {
       all.addAll(consumers(i));
@@ -276,6 +282,7 @@ public Set<GraphOperation> consumers() {
    * Get the number of control inputs for this op.
    */
   public int numControlInputs() {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       return TF_OperationNumControlInputs(getUnsafeNativeHandle());
     }
@@ -285,6 +292,7 @@ public int numControlInputs() {
    * Get the control inputs of this op.
    */
   public Set<GraphOperation> controlInputs() {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       int numInputs = numControlInputs();
       PointerPointer<TF_Operation> handles = new PointerPointer<>(numInputs);
@@ -305,6 +313,7 @@ public Set<GraphOperation> controlInputs() {
    * Get the number of ops with this op as a control dependency.
    */
   public int numControlConsumers() {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       return TF_OperationNumControlOutputs(getUnsafeNativeHandle());
     }
@@ -314,6 +323,7 @@ public int numControlConsumers() {
    * Get the ops with this op as a control dependency.
    */
   public Set<GraphOperation> controlConsumers() {
+    requireHandle(unsafeNativeHandle);
     try (PointerScope scope = new PointerScope()) {
       int numConsumers = numControlConsumers();
       PointerPointer<TF_Operation> handles = new PointerPointer<>(numConsumers);