containsElement method
Implementation
bool containsElement(T element) {
if (empty) {
return false;
}
final isLowerBoundSatisfied = _isBoundSatisfied(lowerBound, element);
final isUpperBoundSatisfied = _isBoundSatisfied(upperBound, element);
return isLowerBoundSatisfied && isUpperBoundSatisfied;
}