o check. The
      macro generates a metafunction called "has_member_function_'name_of_inner_member_function'".
    </p>
<p>
      The metafunction can be invoked in two different ways.
    </p>
<p>
      The first way of invoking the metafunction is by passing it the enclosing type
      to introspect and a signature for the member function as a series of separate
      template arguments. The signature for the member function consists of the template
      arguments of a return type, of optional parameter