code: function(event_name, fn, context, listener_args) {
  
  		return this._addListener(event_name, fn, context, listener_args, this._listeners)
  
  	}
docs: Add listener for event `event_name`
  
  @param {string} event_name Name of the event to listen to
  @param {function} fn The callback
  @param {Object} context The context for callback execution (an object, to which the callback belongs)
  @param {*} [listener_args] Static listener arguments. May be usable when one callback responds to different events
  @returns {_tListener} Listener structure, which later may be suspended, or removed via call to {@link Lava.mixin.Observable#removeListener}