em

~~

**type**: ``string`` **default**: the default entity manager

**type**: ``string``| ``Doctrine\Common\Persistence\ObjectManager``**default**: the default entity manager

If specified, the specified entity manager will be used to load the choices

instead of the default entity manager.

choices

**type**: array || ``\Traversable`` **default**: ``null``

**type**: array | ``\Traversable`` **default**: ``null``

Instead of allowing the `class`_ and `query_builder`_ options to fetch the

entities to include for you, you can pass the ``choices`` option directly.