Symbiote\ArrayListExportable
Used in place of ArrayList when preparing nested arrays for export for SS templates.
var_export calls '__set_state' on classes, so it produces code like:
ArrayList::__set_state(array('items' => [...]))
And because ArrayList doens't implement '__set_state', executing the code throws errors.
So we work around this by using an ArrayListExportable to produce:
ArrayListExportable::__set_state(array('items' => [...]))
And implement '__set_state' to return a constructed ArrayList.