<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def permissions(self):
 """ A list of strings describing permissions. See Facebook's exhaustive `Permissions Reference <http://developers.facebook.com/docs/authentication/permissions/>`_ for a list of available permissions. """

        response = self.graph.get('%s/permissions' % self.id)

        permissions = []
        for permission, state in response['data'][0].items():
            permissions.append(permission)
        
        return permissions