code: func IsUnknownInstruction(err error) bool {
  	_, ok := err.(*UnknownInstruction)
  	if !ok {
  		var pe *parseError
  		if pe, ok = err.(*parseError); ok {
  			_, ok = pe.inner.(*UnknownInstruction)
  		}
  	}
  	return ok
  }
docs: // IsUnknownInstruction checks if the error is an UnknownInstruction or a parseError containing an UnknownInstruction