class NumberChecker:
def between(self, num, low_num=0, high_num=None):
if high_num is None:
low_num, high_num = 0, low_num
return low_num <= num <= high_num
checker = NumberChecker()
print(checker.between(5, 0, 10))
print(checker.between(5, 10))
print(checker.between(5, high_num=20))