stant specifies the maximum argument length for the constructor templates.
      The constant may be overridden if more (or less) argument configurations are
      needed. The constant may be read for code that is expandable like the class
      template and needs to maintain the same maximum size. (Example code would be
      a class that uses this class template as a base class for a member with a flexible
      set of constructors.) This constant is ignored when C++11 features are present.
    </p>
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