'Register an event handler to be called first for an event.
All event handlers registered with ``register_first()`` will
be called before handlers registered with ``register()`` and
``register_last()``.'

def register_first(self, event_name, handler, unique_id=None, unique_id_uses_count=False):

    self._verify_and_register(event_name, handler, unique_id, register_method=self._register_first, unique_id_uses_count=unique_id_uses_count)
