code: func isNonstandardTransaction(tx *btcutil.Tx) bool {
  	// Check all of the output public key scripts for non-standard scripts.
  	for _, txOut := range tx.MsgTx().TxOut {
  		scriptClass := txscript.GetScriptClass(txOut.PkScript)
  		if scriptClass == txscript.NonStandardTy {
  			return true
  		}
  	}
  	return false
  }
docs: // isNonstandardTransaction determines whether a transaction contains any
  // scripts which are not one of the standard types.