@API(status = API.Status.STABLE)
    public boolean isPresent(final @NonNull CommandFlag<Void> flag) {
        return this.isPresent(flag.name());
    }
Check whether a presence flag is present. This will return {@code false}
for all value flags.

@param flag A presence flag instance
@return {@code true} if the flag is a presence flag and is present,
        else {@code false}
cloud-core/src/main/java/org/incendo/cloud/parser/flag/FlagContext.java