title: How to determine protobuf version of Protobuf object?
body: <p>My project assumes Proto3 Objects as input.
  But, sometimes users provide Proto2 Object as input. In those cases, we want to throw exception as our code works with only Proto3 classes.</p>
  
  <p>How can we check if input Protobuf object provided is Proto2 or Proto3 ?</p>
  
  <p>Checking for method presence or default values is kind of a Hack.
  Is there any proper method to check version of Protobuf Object ?</p>