Returns an object that corresponds to given query or ``None``.

        Example::

            item = Item.get_one(db, {'title': u'Hello'})

def get_one(cls, db, *args, **kwargs):
        """
        Returns an object that corresponds to given query or ``None``.

        Example::

            item = Item.get_one(db, {'title': u'Hello'})

        """
        data = db[cls.collection].find_one(*args, **kwargs)
        if data:
            return cls.wrap_incoming(data, db)
        else:
            return None