default FunctionalCommandBuilder<T> assertSender(Predicate<T> test) {
        return assertSender(test, DEFAULT_INVALID_SENDER_MESSAGE);
    }
Tests the sender with the provided predicate.

The default failure message is sent if the sender does not pass the predicate.

@param test the test predicate
@return the builder instance
helper/src/main/java/me/lucko/helper/command/functional/FunctionalCommandBuilder.java