"tf.IfRegion"(%0) ( {
      %2 = "tf.A"() : () -> (tensor<f32>)
      "tf.Yield"() : () -> ()
      }, {
      "tf.Yield"() : () -> ()
     }) { is_stateless = true } : (tensor<i1>) -> ()
    "tf.IfRegion"(%0) ( {
      %2 = "tf.B"() : () -> (tensor<f32>)
      "tf.Yield"() : () -> ()
      }, {
      "tf.Yield"() : () -> ()
      }) { is_stateless = true } : (tensor<i1>) -> ()
    ```

      // each region and the use of TensorList returned using YieldOp.
      if (auto while_region = llvm::dyn_cast<WhileRegionOp>(use.getOwner())) {
        DCOMMENT("\tTL WhileRegion");
        for (auto branch : while_region.getRegions())
          add_to_worklist(branch->getArgument(use.getOperandNumber()));
        continue;
      }
      if (auto yield = llvm::dyn_cast<YieldOp>(use.getOwner())) {

	case *body:
		v.registerOnHitEOF(fn)
	default:
		panic("unexpected type " + fmt.Sprintf("%T", rc))
	}
}

// requestBodyRemains reports whether future calls to Read
// on rc might yield more data.
func requestBodyRemains(rc io.ReadCloser) bool {
	if rc == NoBody {
		return false
	}
	switch v := rc.(type) {
	case *expectContinueReader:
		return requestBodyRemains(v.readCloser)