call method
Implementation
@override
String? call(TerminalKeyboardEvent event) {
if (event.type == TerminalKeyEventType.release) return null;
if (event.ctrl || event.alt || event.shift) return null;
final index = event.key.index - TerminalKey.f13.index;
if (index < 0 || index >= _sequences.length) return null;
return _sequences[index];
}