<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_user_id(self, provider, info):
        "Return unique identifier from the profile info."
        id_key = self.provider_id or 'id'
        result = info
        try:
            for key in id_key.split('.'):
                result = result[key]
            return result
        except KeyError:
            return None