code: function(pluginName) {
  		
  		var plugin = $.tooltipster._plugin(pluginName);
  		
  		if (plugin) {
  			
  			// if there is a constructor for instances
  			if (plugin.instance) {
  				
  				// proxy non-private methods on the instance to allow new instance methods
  				$.tooltipster.__bridge(plugin.instance, this, plugin.name);
  			}
  		}
  		else {
  			throw new Error('The "'+ pluginName +'" plugin is not defined');
  		}
  		
  		return this;
  	}
docs: Used at instantiation of the plugin, or afterwards by plugins that activate themselves
  on existing instances
  
  @param {object} pluginName
  @returns {self}
  @protected