code: function context(self, method) {
    if (self instanceof Primus) return;
  
    var failure = new Error('Primus#'+ method + '\'s context should called with a Primus instance');
  
    if ('function' !== typeof self.listeners || !self.listeners('error').length) {
      throw failure;
    }
  
    self.emit('error', failure);
  }
docs: Context assertion, ensure that some of our public Primus methods are called
  with the correct context to ensure that
  
  @param {Primus} self The context of the function.
  @param {String} method The method name.
  @api private