### Question:
Graph implements ExecutionEnvironment, AutoCloseable { public void importGraphDef(GraphDef graphDef) throws IllegalArgumentException { importGraphDef(graphDef, ""); } 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 failImportOnInvalidGraphDefs() { try (Graph g = new Graph()) { try { g.importGraphDef(null); } catch (IllegalArgumentException e) { } } }