Users want to get rounding mode in `quantileExact` equivalent to "median_low" from Python:
https://docs.python.org/3/library/statistics.html#statistics.median_low
while current implementation works equivalent to "median_high" (?)
{
        if (!array.empty())
        {
            size_t prev_n = 0;
            for (size_t i = 0; i < size; ++i)
            {
                auto level = levels[indices[i]];
                size_t n = level < 1
                    ? level * array.size()
                    : (array.size() - 1);
                std::nth_element(array.begin() + prev_n, array.begin() + n, array.end());
                result[indices[i]] = array[n];
                prev_n = n;
            }
        }
        else
        {
            for (size_t i = 0; i < size; ++i)
                result[i] = Value();
        }
    }
};
template <typename Value>
struct QuantileExactExclusive : public QuantileExact<Value>
{
    using QuantileExact<Value>::array;
    
    Float64 getFloat(Float64 level)