public OwinResponse(IDictionary<string, object> environment) {
     if (environment == null) {
         throw new ArgumentNullException("environment");
     }
     _environment = environment;
     var headers = _environment.GetValueOrCreate(OwinKeys.Response.Headers, OwinFactory.CreateHeaders);
     _headers = new OwinResponseHeaders(headers);
 }
        public OwinResponse(IDictionary <string, object> environment)
        {
            if (environment == null)
            {
                throw new ArgumentNullException("environment");
            }
            _environment = environment;
            var headers = _environment.GetValueOrCreate(OwinKeys.Response.Headers, OwinFactory.CreateHeaders);

            _headers = new OwinResponseHeaders(headers);
        }