Can't use ForceAuthn attribute in the Authn request

[ChananM]

I'm trying to use the client for identity provider redirection, and force authentication in the provider
What I need is to add ForceAuthn="true" to the saml2p:AuthnRequest tag, but I don't see any way to do it in the client. I'm using the client as follows:

SamlClient client = new SamlClient(relyingPartyIdentifier assertionConsumerService, identityProviderUrl, responseIssuer, certs, SamlClient.SamlIdpBinding.POST); 
client.getSamlRequest();
client.redirectToIdentityProvider(response, customerId);

And I can see the ForceAuthn attribute exists in the lib code, but I didn't find how to use it