checkValidInputRange function
Implementation
void checkValidInputRange(List<num> arr) {
assert(arr.length >= 2, 'inputRange must have at least 2 elements');
for (var i = 1; i < arr.length; ++i) {
assert(
arr[i] >= arr[i - 1],
'inputRange must be monotonically non-decreasing $arr',
);
}
}