code: protected static Interceptor addInterceptor( InterceptorConfig config,
                                                   Class baseClassOrInterface,
                                                   List/*< Interceptor >*/ interceptors )
      {
          Interceptor interceptor = createInterceptor( config, baseClassOrInterface );
          if ( interceptor != null )
              interceptors.add( interceptor );
          return interceptor;
      }
docs: Instantiates an interceptor, based on the class name in the given InterceptorConfig, and adds it to the
  given collection of interceptors.
  
  @param config the InterceptorConfig used to determine the interceptor class.
  @param baseClassOrInterface the required base class or interface.  May be <code>null</code>.
  @param interceptors the List of interceptors to which to add.
  @return an initialized Interceptor, or <code>null</code> if an error occurred.