It can only be bound to a select type (or subclass thereof), and inherits the configuration
from there as far as possible.
Available configuration options:
- string othertext: The text that is used to separate the main from the
other form element. They are usually displayed in the same line. The value is passed
through the standard schema localization chain.
Note: At this time there is no support for select types with allow_other set at this time.
string $othertext
l10n string id or direct text to use to separate the others input field from
the main select.
Applies only for types which have allow_other set.
string $render_mode
Controls how the selection list show be rendered, 'horizontal' means all choices will be
in one line, 'vertical' means they will be below each other.
'auto' will choose one based
on the number of choices