Org.BouncyCastle.Asn1.Crmf.ProofOfPossession.GetInstance C# (CSharp) Method

        public static ProofOfPossession GetInstance(object obj)
        {
            if (obj is ProofOfPossession)
                return (ProofOfPossession)obj;

            if (obj is Asn1TaggedObject)
                return new ProofOfPossession((Asn1TaggedObject)obj);

            throw new ArgumentException("Invalid object: " + obj.GetType().Name, "obj");
        }

 private CertReqMsg(Asn1Sequence seq)
 {
     certReq = CertRequest.GetInstance(seq[0]);
     for (int i = 1; i < seq.Count; i++)
     {
         object obj = seq[i];
         if (obj is Asn1TaggedObject || obj is ProofOfPossession)
         {
             popo = ProofOfPossession.GetInstance(obj);
         }
         else
         {
             regInfo = Asn1Sequence.GetInstance(obj);
         }
     }
 }