20 General utilities library [utilities]
namespace std {
  template<class Context, class... Args>
  struct format-arg-store {      
    array<basic_format_arg<Context>, sizeof...(Args)> args;
  };
}
An instance of 
format-arg-store stores formatting arguments
.Preconditions: The type
typename Context::template formatter_type<Ti>
meets the 
Formatter requirements (
[formatter.requirements])
for each 
Ti in 
Args. Returns: 
{basic_format_arg<Context>(args)...}. Effects: Equivalent to:
return make_format_args<wformat_context>(args...);