code: func isNullData(pops []parsedOpcode) bool {
  	// A nulldata transaction is either a single OP_RETURN or an
  	// OP_RETURN SMALLDATA (where SMALLDATA is a data push up to
  	// MaxDataCarrierSize bytes).
  	l := len(pops)
  	if l == 1 && pops[0].opcode.value == OP_RETURN {
  		return true
  	}
  
  	return l == 2 &&
  		pops[0].opcode.value == OP_RETURN &&
  		(isSmallInt(pops[1].opcode) || pops[1].opcode.value <=
  			OP_PUSHDATA4) &&
  		len(pops[1].data) <= MaxDataCarrierSize
  }
docs: // isNullData returns true if the passed script is a null data transaction,
  // false otherwise.