public static Optional<MultifactorAuthenticationProvider> resolveProvider(
        final Map<String, MultifactorAuthenticationProvider> providers,
        final String requestMfaMethod) {
        return resolveProvider(providers, Stream.of(requestMfaMethod).collect(Collectors.toList()));
    }
Resolve provider optional.

@param providers        the providers
@param requestMfaMethod the request mfa method
@return the optional
core/cas-server-core-authentication-mfa-api/src/main/java/org/apereo/cas/authentication/MultifactorAuthenticationUtils.java