Problems with facebook login

Hi It seems u folks have changed fb login apis, please help me there is no documentation for new method calls
What will be value for withFacebookSDK and tokenString?

backendless!.userService.login(withFacebookSDK: <#T##String!#>, tokenString: <#T##String!#>, expirationDate: <#T##Date!#>, fieldsMapping: <#T##Any!#>, response: <#T##((BackendlessUser?) -> Void)!##((BackendlessUser?) -> Void)!##(BackendlessUser?) -> Void#>, error: <#T##((Fault?) -> Void)!##((Fault?) -> Void)!##(Fault?) -> Void#>)

Hello,

Please check this documentation. All steps and examples described there.

Regards, Olga