auto subtypes = resource_type.getSubtypes();
  if (subtypes.size() == 1) return subtypes[0];
  return nullptr;
}

// Replaces all `tf.VarIsInitializedOp` in a block with a constant true.
// TODO(b/171039585): Replace this with proper analysis of
// `tf.VarIsInitializedOp` in regards to resource writes and control flow.
void SetAllVarIsInitializedToTrue(Block* block) {
  auto builder = OpBuilder::atBlockBegin(block);

// VarIsInitializedOp
//===----------------------------------------------------------------------===//

namespace {

/// Erase VarIsInitializedOp operations with no uses. This op has side effect on
/// resources (read-only), but can still be deleted if it has zero uses.
struct EraseDeadVarIsInitializedOp
    : public OpRewritePattern<VarIsInitializedOp> {

  %is = "tf.VarIsInitializedOp"(%vh) : (tensor<!tf_type.resource<tensor<f32>>>) -> tensor<i1>
  %res = "tf.UnknownOp"(%vh) : (tensor<!tf_type.resource<tensor<f32>>>) -> tensor<i1>
  func.return %res : tensor<i1>
}
// Unused VarIsInitializedOp is erased.
// CHECK: tf.VarHandleOp
// CHECK-NEXT: tf.UnknownOp

  );

  TF_DerivedOperandTypeAttr T = TF_DerivedOperandTypeAttr<0>;
  TF_DerivedResultTypeAttr out_type = TF_DerivedResultTypeAttr<0>;
}

def TF_VarIsInitializedOp : TF_Op<"VarIsInitializedOp", []> {
  let summary = [{
Checks whether a resource handle-based variable has been initialized.
  }];

  let arguments = (ins