eterSpec</span></a> enumerates the required and optional parameters in
their positional order, along with any type requirements (note that
it does <em>not</em> specify defaults -- those will be dealt with
separately):</p>
<pre class="literal-block">
namespace boost { namespace python {

using boost::mpl::_;

typedef parameter::parameters&lt;
    required&lt;tag::class_type, boost::is_class&lt;_&gt; &gt;
  , parameter::optional&lt;tag::base_list, mpl::is_sequence&lt;_&gt; &gt;
  , parameter::optional&lt;tag: