/// <summary>
        /// Imports the certificate(s) from the specified stream.
        /// </summary>
        /// <remarks>
        /// Imports the certificate(s) from the specified stream.
        /// </remarks>
        /// <param name="stream">The stream to import.</param>
        /// <exception cref="System.ArgumentNullException">
        /// <paramref name="stream"/> is <c>null</c>.
        /// </exception>
        /// <exception cref="System.IO.IOException">
        /// An error occurred reading the stream.
        /// </exception>
        public void Import(System.IO.Stream stream)
        {
            if (stream == null)
            {
                throw new System.ArgumentNullException(nameof(stream));
            }

            Org.BouncyCastle.X509.X509CertificateParser parser =
                new Org.BouncyCastle.X509.X509CertificateParser();

            foreach (Org.BouncyCastle.X509.X509Certificate certificate in parser.ReadCertificates(stream))
            {
                if (unique.Add(certificate))
                {
                    certs.Add(certificate);
                }
            }
        }