title: expose public struct inside a class for boost::python
body: <p>I want to use this C++ class over python code with boost::python </p>
  
  <pre><code>/* creature.h */
  class Human {
  private:
  public:
      struct emotion {
          /* All emotions are percentages */
          char joy;
          char trust;
          char fear;
          char surprise;
          char sadness;
          char disgust;
          char anger;
          char anticipation;
          char love;
      };
  };
  </code></pre>
  
  <p>the question is how to expose this public attribute in boost-python</p>
  
  <pre><code>namespace py = boost::python;
  
  BOOST_PYTHON_MODULE(example)
  {
      py::class_&lt;Human&gt;("Human");
          // I have not idea how put the public struct here
  }
  </code></pre>