Is Paragraph 21(6) of the Gesetz über die Beteiligung der Arbeitnehmer in einer Europäischen Gesellschaft (German Law on involvement of employees in a European company), which determines that, in the case where an SE [Societas Europaea; European Company] with its registered office in Germany is established by means of transformation, a separate selection procedure for persons nominated by trade unions for a certain number of supervisory board members representing the employees must be guaranteed, compatible with Article 4(4) of Council Directive 2001/86/EC of 8 October 2001 supplementing the Statute for a European company with regard to the involvement of employees?