     public func response(completionHandler: ( (RType.ValueType, NSData)?, CallError<EType.ValueType>?) -> Void) -> Self {
         self.request.validate().response {
             (request, response, dataObj, error) -> Void in
-            let data = dataObj as! NSData
+            let data = dataObj as NSData!
             if error != nil {
                 completionHandler(nil, self.handleResponseError(response, data: data))
             } else {
                 let result = response!.allHeaderFields["Dropbox-Api-Result"] as! String
                 let resultData = result.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!
                 let resultObject = self.responseSerializer.deserialize(parseJSON(resultData))
-                
+
                 completionHandler( (resultObject, data), nil)
             }
         }

            return (mutableRequest, nil)
        }))
    }
    
    /// Called when a request completes.
    ///
    /// :param: completionHandler A closure which takes a (response, error) and handles the result of the call appropriately.
    public func response(completionHandler: (RType.ValueType?, CallError<EType.ValueType>?) -> Void) -> Self {
        self.request.validate().response {
            (request, response, dataObj, error) -> Void in
            let data = dataObj as! NSData
            if error != nil {
                completionHandler(nil, self.handleResponseError(response, data: data))
            } else {

            esc = "\(char)"
        }
        out += esc

    }
    return out
}
