def METHOD_NAME(values: TimeValues, value_to_date: Callable, date_to_value: Callable, time_unit: Union[int, timedelta]) -> TimeValues:
    try:
        intervals = []
        # populate list of intervals based on original date/week values
        for v in values:
            if isinstance(v, int):
                # 20200101 -> [20200101, 20200101]
                intervals.append([value_to_date(v), value_to_date(v)])
            else: # tuple
                # (20200101, 20200102) -> [20200101, 20200102]
                intervals.append([value_to_date(v[0]), value_to_date(v[1])])
        intervals.sort()
        # merge overlapping intervals https://leetcode.com/problems/merge-intervals/
        merged = []
        for interval in intervals:
            # no overlap, append the interval
            # caveat: we subtract 1 from interval[0] so that contiguous intervals are considered overlapping. i.e. [1, 1], [2, 2] -> [1, 2]
            if not merged or merged[-1][1] < interval[0] - time_unit:
                merged.append(interval)
            # overlap, merge the current and previous intervals
            else:
                merged[-1][1] = max(merged[-1][1], interval[1])
        # convert intervals from dates/weeks back to integers
        ranges = []
        for m in merged:
            if m[0] == m[1]:
                ranges.append(date_to_value(m[0]))
            else:
                ranges.append((date_to_value(m[0]), date_to_value(m[1])))
        get_structured_logger('server_utils').debug("Optimized list of date values", original=values, optimized=ranges, original_length=len(values), optimized_length=len(ranges))
        return ranges
    except Exception as e:
        get_structured_logger('server_utils').debug('bad input to date ranges', time_values=values, exception=e)
        return values