assertFactor function
Assert that the factor value is somewhere from 0 - 100.
Will throw InvalidValueRangeException if not in range.
Implementation
void assertFactor(int factor) {
const range = (lower: 0, upper: 100);
if (_inRange(range: range, value: factor)) return;
throw InvalidValueRangeException(
value: factor,
range: range,
);
}