checkLt function
Asserts that value is less than limit.
Throws an AssertionError using label as a descriptive name for value.
Implementation
void checkLt(final int value, final int limit, [final Object? label]) {
  if (value >= limit) {
    throw AssertionError(
      'The ${label ?? 'value'} $value must be `less than` $limit.',
    );
  }
}