public static ValueTask <decimal> SumAsync(this IAsyncEnumerable <decimal> source) =>
 LinqEnumerable.SumAsync(source);
 public static ValueTask <float?> SumAsync(this IAsyncEnumerable <float?> source) =>
 LinqEnumerable.SumAsync(source);
 public static ValueTask <int> SumAsync(this IAsyncEnumerable <int> source) =>
 LinqEnumerable.SumAsync(source);
 public static ValueTask <double?> SumAsync <TSource>(this IAsyncEnumerable <TSource> source, Func <TSource, double?> selector) =>
 LinqEnumerable.SumAsync(source, selector);