Example code for ext:container issue

example.php

// Collapse Container

\TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\B13\Container\Tca\Registry::class)->configureContainer(
    (
    new \B13\Container\Tca\ContainerConfiguration(
        'container-collapse', // CType
        'Collapse', // label
        'Description', // description
        [
            [
                [
                    'name'                     => 'Content',
                    'colPos'                   => 1001,
                    'allowed'                  => ['CType' => 'container-element'],
                ]
            ]
        ]
    )
    )->setIcon('content-accordion')
);

// Container Elemnt (element inside the collapse)

\TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\B13\Container\Tca\Registry::class)->configureContainer(
    (
    new \B13\Container\Tca\ContainerConfiguration(
        'container-element', // CType
        'Container Element', // label
        'description', // description
        [
            [
                [
                    'name'       => 'Content',
                    'colPos'     => 4001,
                ]
            ]
        ]
    )
    )->setIcon('content-container-columns-1')
);