// TODO: Change this description!
                            /**
                            Provides a Panel widget, a widget that mimics the functionality of a regular OS
                            window. Comes with Standard Module support, XY Positioning, Alignment Support,
                            Stack (z-index) support, modality, auto-focus and auto-hide functionality, and
                            header/footer button support.
                            
                            @module panel
                            **/
                            
                            var getClassName = Y.ClassNameManager.getClassName;
                            
                            // TODO: Change this description!
                            /**
                            A basic Panel Widget, which can be positioned based on Page XY co-ordinates and
                            is stackable (z-index support). It also provides alignment and centering support
                            and uses a standard module format for it's content, with header, body and footer
                            section support. It can be made modal, and has functionality to hide and focus
                            on different events. The header and footer sections can be modified to allow for
                            button support.
                            
                            @class Panel
                            @constructor
                            @extends Widget
                            @uses WidgetAutohide
                            @uses WidgetButtons
                            @uses WidgetModality
                            @uses WidgetPosition
                            @uses WidgetPositionAlign
                            @uses WidgetPositionConstrain
                            @uses WidgetStack
                            @uses WidgetStdMod
                            @since 3.4.0
                             */
                            Y.Panel = Y.Base.create('panel', Y.Widget, [
                                // Other Widget extensions depend on these two.
                                Y.WidgetPosition,
                                Y.WidgetStdMod,
                            
                                Y.WidgetAutohide,
                                Y.WidgetButtons,
                                Y.WidgetModality,
                                Y.WidgetPositionAlign,
                                Y.WidgetPositionConstrain,
                                Y.WidgetStack
                            ], {
                                // -- Public Properties ----------------------------------------------------
                            
                                /**
                                Collection of predefined buttons mapped from name => config.
                            
                                Panel includes a "close" button which can be use by name. When the close
                                button is in the header (which is the default), it will look like: [x].
                            
                                See `addButton()` for a list of possible configuration values.
                            
                                @example
                                    // Panel with close button in header.
                                    var panel = new Y.Panel({
                                        buttons: ['close']
                                    });
                            
                                    // Panel with close button in footer.
                                    var otherPanel = new Y.Panel({
                                        buttons: {
                                            footer: ['close']
                                        }
                                    });
                            
                                @property BUTTONS
                                @type Object
                                @default {close: {}}
                                @since 3.5.0
                                **/
                                BUTTONS: {
                                    close: {
                                        label  : 'Close',
                                        action : 'hide',
                                        section: 'header',
                            
                                        // Uses `type="button"` so the button's default action can still
                                        // occur but it won't cause things like a form to submit.
                                        template  : '<button type="button" />',
                                        classNames: getClassName('button', 'close')
                                    }
                                }
                            }, {
                                ATTRS: {
                                    // TODO: API Docs.
                                    buttons: {
                                        value: ['close']
                                    }
                                }
                            });