Get a list of the names of all subscribed music services.

        Returns:
            list: A list of strings.

def get_subscribed_services_names(cls):
        """Get a list of the names of all subscribed music services.

        Returns:
            list: A list of strings.
        """
        # This is very inefficient - loops within loops within loops, and
        # many network requests
        # Optimise it?
        accounts_for_service = Account.get_accounts_for_service
        service_data = cls._get_music_services_data().values()
        return [
            service['Name'] for service in service_data
            if len(
                accounts_for_service(service['ServiceType'])
            ) > 0
        ]