/**
  * Adds the current context to this implementations set of contexts
  * @return    string    Hashed context identifier
  */
 public function add_context($flavor = null)
 {
     list($m_context, $h_context) = FBMLContext::marshall_($flavor ? $flavor : $this->_flavor);
     $this->_contexts[$h_context] = $m_context;
     return $h_context;
 }