def generateImplicitParameters(cls, obj):
        """
        Create PRODID, VERSION, and VTIMEZONEs if needed.

        VTIMEZONEs will need to exist whenever TZID parameters exist or when
        datetimes with tzinfo exist.
        """
        if not hasattr(obj, 'version'):
            obj.add(ContentLine('VERSION', [], cls.versionString))