public static MethodInfo Sum_NullableInt64_TSource_2(Type TSource) =>
(s_Sum_NullableInt64_TSource_2 ??
(s_Sum_NullableInt64_TSource_2 = new Func<IQueryable<object>, Expression<Func<object, long?>>, long?>(Queryable.Sum).GetMethodInfo().GetGenericMethodDefinition()))
.MakeGenericMethod(TSource);