def _find_index(self, target_page: int) -> Tuple[(int, bool)]:
    result_idx = None
    for (idx, (page, _)) in enumerate(self._values):
        if (page > target_page):
            break
        result_idx = idx
    if (result_idx is None):
        raise ValueError(f'Page Property indexed with negative index: {target_page}')
    return (result_idx, (self._values[result_idx][0] == target_page))
def _find_index(self, target_page: int) -> Tuple[(int, bool)]:
    result_idx = None
    for (idx, (page, _)) in enumerate(self._values):
        if (page > target_page):
            break
        result_idx = idx
    if (result_idx is None):
        raise ValueError(f'Page Property indexed with negative index: {target_page}')
    return (result_idx, (self._values[result_idx][0] == target_page))