<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_subscription_labels(self, userPk):
 """Returns a list with all the labels the user is subscribed to"""

        r = self._request('subscriptions/' + str(userPk))
        if r:
            s = r.json()
            return s
        return []