Create a new entity.

        The entity will have a higher UID than any previously associated
        with this world.

        :return: the new entity
        :rtype: :class:`essence.Entity`

def create_entity(self):
        """Create a new entity.

        The entity will have a higher UID than any previously associated
        with this world.

        :return: the new entity
        :rtype: :class:`essence.Entity`"""
        self._highest_id_seen += 1
        entity = Entity(self._highest_id_seen, self)
        self._entities.append(entity)
        return entity