SilverStripe SS4 extending page

<?php

namespace SilverStripe\Masters;

use Page;
use SilverStripe\Assets\Image;
use SilverStripe\AssetAdmin\Forms\UploadField;
use SilverStripe\Forms\CheckboxSetField;
use SilverStripe\Forms\DropdownField;
use SilverStripe\Forms\HeaderField;
use SilverStripe\Forms\TextareaField;
use SilverStripe\Forms\TextField;

class HeaderSection extends Page {

    private static $singular_name = 'Header Section';
    private static $plural_name = 'Headers Sections';
    private static $description = 'Headers section part to be used in upper part of page.';
    private static $icon = '';

    private static $db = [
        'Maintitle' => 'Varchar(128)',
        'Subtitle' => 'Varchar(128)',
        'Kicker' => 'Varchar(128)',
        'LeadContent' => 'HTMLText',
        'Jumbotron' => "Enum('None,Graphical,BackgroundImage,Graphical-Full,BackgroundImage-Full','None')",
        'Inverse' => 'Boolean',
        'ElementClass' => 'Varchar(192)',
        'SubElementClass' => 'Varchar(192)',
        'RowExtraClass' => 'Varchar(192)',
        'MainContentClass' => 'Varchar(192)',
        'JumbotronClass' => 'Varchar(192)',
        'ContainerFluid' => 'Boolean',
        'TitleClass' => 'Varchar(192)',
        'HideTitles' => 'Boolean',
        'SubtitleClass' => 'Varchar(192)',
        'KickerClass' => 'Varchar(192)',
        'LeadContentClass' => 'Varchar(192)'
    ];

    private static $has_one = [
        'MainImage' => Image::class,
        'BackgroundImage' => Image::class
    ];

    private static $defaults = [
        'MainContentClass' => 'col-md-12',
        'ContainerFluid' => '0',
        'JumbotronClass' => 'col-md-12',
        'ElementClass' => '',
        'LeadContentClass' => '',
        'KickerClass' => '',
        'TitleClass' => '',
        'SubtitleClass' => ''
    ];

    private function getJumbotronStyle() {
        return array(
            'None' => _t('Content.JUMBOTRONNONE', 'None'),
            'Graphical' => _t('Content.JUMBOTRONGRAPHICAL', 'Graphical'),
            'BackgroundImage' => _t('Content.JUMBOTRONBACKGROUNDIMAGE', 'Background image'),
            'Graphical-Full' => _t('Content.JUMBOTRONGRAPHICALFULL', 'Full sized graphical element'),
            'BackgroundImage-Full' => _t('Content.JUMBOTRONBACKGROUNDIMAGEFULL', 'Full sized background image')
        );
    }

    function getCMSFields() {

        // Settings for UploadFields : Main Image

        $UploadField = UploadField::create("MainImage", _t('Content.MAINIMAGE','Main image'));
        $UploadField
            ->setFolderName('Uploads/images/mainimages/')
            ->setDisplayFolderName('Uploads/images/mainimages/')
            ->getValidator()->setAllowedExtensions(array('jpg', 'gif', 'png'));

        $UploadField2 = UploadField::create("BackgroundImage", _t('Content.ELEMENTBACKGROUNDIMAGE','Element backgroundimage'));
        $UploadField2
            ->setFolderName('Uploads/images/backgrounds/')
            ->setDisplayFolderName('Uploads/images/backgrounds/')
            ->getValidator()->setAllowedExtensions(array('jpg', 'gif', 'png'));


        $fields = parent::getCMSFields();

        $fields->findOrMakeTab('Root.Main', _t('Content.TABHEADER','Header'));
        $fields->addFieldsToTab('Root.Main', [

            HeaderField::create(_t('Content.MASTERHEADING','Masterheading')),
            TextField::create("Kicker", _t('Content.KICKER','Kicker text before title'))
                ->setDescription(_t('Content.KICKERHELP','Small introduction text')),
            TextField::create("Maintitle", _t('Content.MAINTITLE','Main title'))
                ->setDescription(_t('Content.MAINTITLEHELP','If used, overrides page name.')),
            CheckboxField::create('HideTitles', _t('Content.HIDETITLES','Hide titles?'))
                ->setDescription(_t('Content.HIDETITLESHELP','Hide Maintitle and Master heading')),
            TextField::create("Subtitle", _t('Content.SUBTITLE','Subtitle under the title')),
            $leadContentField = HtmlEditorField::create('LeadContent', _t('Content.LEADCONTENT','Introduction content'))
                ->setDescription(_t('Content.LEADCONTENTHELP','Write short and effective lead text about the content. Change style, if needed.')),
            HeaderField::create(_t('Content.IMAGES','Images')),
            $UploadField->setDescription(_t('Content.MAINIMAGEHELP','Includes automatic scaling for image.')),
            $UploadField2->setDescription(_t('Content.ELEMENTBACKGROUNDIMAGEHELP','Use for big backgrounds in element.')),
            HeaderField::create(_t('Content.CONTENT','Main content in one column'))
        ], 'Content');

        $fields->findOrMakeTab('Root.Main', _t('Content.TABHEADER','Header'));
        $fields->addFieldsToTab('Root.Main', [
            TextField::create("MainContentClass", _t('Content.MAINCONTENTCLASS','Page content class'))
                ->setDescription(_t('Content.MAINCONTENTCLASSHELP','You can use Bootstrap grid classes. Default value: col-md-12 To center content: text-center'))
        ]);

        $fields->findOrMakeTab('Root.OPTIONS', _t('Content.TABOPTIONS','Options'));
        $fields->addFieldsToTab('Root.OPTIONS', [
            HeaderField::create(_t('Content.PAGESTYLING','Settings for page layout')),
            TextField::create("ElementClass", _t('Content.ELEMENTCLASS','Bootstrap class for element'))
                ->setDescription(_t('Content.ELEMENTCLASSHELP','Usage e.g. block-fill-height block-fill-height-half text-center etc.')),
            TextField::create("SubElementClass", _t('Content.SUBELEMENTCLASS','Bootstrap class for subelement'))
                ->setDescription(_t('Content.SUBELEMENTCLASSHELP','Next to Block-element. Usage e.g. block-xs-middle block-md-bottom etc.')),
            CheckboxField::create('ContainerFluid', _t('Content.CONTAINERFLUID','Fluid Container?'))
                ->setTitle (_t('Content.CONTAINERFLUIDTITLE','Fluid container?'))
                ->setName ('ContainerFluid')
                ->setDescription(_t('Content.CONTAINERFLUIDHELP','Makes element full width with Bootstrap container-fluid class.')),
            TextField::create("RowExtraClass", _t('Content.ROWEXTRACLASS','Extra row class'))
                ->setDescription(_t('Content.ROWEXTRACLASSHELP','Add extra class for Bootstrap row, like row-valign-middle')),
            HeaderField::create(_t('Content.MASTERHEADSTYLING','Masterheading styling options')),
            DropdownField::create('Jumbotron', _t('Content.JUMBOTRON', 'Jumbotron'), $this->getJumbotronStyle())
                ->setDescription(_t('Content.JUMBOTRONHELP','Specify, do you need jumbotron element and in what style.')),
            TextField::create("JumbotronClass", _t('Content.JUMBOTRONCLASS','Jumbotron css-class'))
                ->setDescription(_t('Content.JUMBOTRONCLASSHELP','Used for col-xx-x (default col-md-12)')),
            CheckboxField::create('Inverse', _t('Content.INVERSE','Inverse?'))
                ->setDescription(_t('Content.INVERSEHELP','Light text over dark background')),
            HeaderField::create(_t('Content.MASTERHEADTYPOGRAPHY','Masterhead typography styling options')),
            TextField::create("TitleClass", _t('Content.TITLECLASS','Title css-class'))
                ->setDescription(_t('Content.TITLECLASSHELP','Usage e.g. block-title text-muted text-uppercase')),
            TextField::create("KickerClass", _t('Content.KICKERCLASS','Kicker css-class'))
                ->setDescription(_t('Content.KICKERCLASSHELP','Usage e.g. text-muted text-uppercase')),
            TextField::create("SubtitleClass", _t('Content.SUBTITLECLASS','Subtitle css-class'))
                ->setDescription(_t('Content.SUBTITLECLASSHELP','Usage e.g. text-muted text-uppercase')),
            TextField::create("LeadContentClass", _t('Content.LEADCONTENTCLASS','Lead content css-class'))
                ->setDescription(_t('Content.LEADCONTENTCLASSHELP','Usage e.g. text-muted'))
        ]);
        $leadContentField->addExtraClass('stacked')->setRows(3);

    return $fields;

    }

}