isSubCmd function
check cmd has valid subCmdNames
Implementation
bool isSubCmd(String cmd, List<String> subCmdNames) {
var parts = cmd.split(' ');
if (parts.length < 2) return false;
final [cmdName, subName, ...] = parts;
if (cmdName != 'ft' || !subCmdNames.contains(subName.trim())) return false;
return true;
}