Proguard rules about fiskaly-kassensichv-client-java

After adding:
-keep class com.fiskaly.kassensichv.** { *; }

I learned more info about the problem:

    java.lang.UnsatisfiedLinkError: No implementation found for void d.a.a() (tried Java_d_a_a and Java_d_a_a__)
        at d.a.a(Native Method)
        at d.a.<clinit>(SourceFile:38)
        at d.a.b(SourceFile:50)
        **at com.fiskaly.kassensichv.sma.Sma.<clinit>(SourceFile:11)**
        **at com.fiskaly.kassensichv.sma.Sma.invoke(Native Method)**
        **at com.fiskaly.kassensichv.sma.AndroidSma.invoke(SourceFile:6)**
        **at com.fiskaly.kassensichv.client.interceptors.TransactionInterceptor.signTransaction(SourceFile:49)**
        **at com.fiskaly.kassensichv.client.interceptors.TransactionInterceptor.intercept(SourceFile:147)**
        at okhttp3.E.d.g.a(SourceFile:112)
        at okhttp3.E.d.g.a(SourceFile:87)
        at com.fiskaly.kassensichv.client.interceptors.AuthenticationInterceptor.intercept(SourceFile:49)
        at okhttp3.E.d.g.a(SourceFile:112)
        at okhttp3.E.d.g.a(SourceFile:87)
        at com.fiskaly.kassensichv.client.interceptors.HeaderInterceptor.intercept(SourceFile:23)
        at okhttp3.E.d.g.a(SourceFile:112)
        at okhttp3.E.d.g.a(SourceFile:87)
        at okhttp3.x.c(SourceFile:184)
        at okhttp3.x.a(SourceFile:66)

It comes from this class:

package com.fiskaly.kassensichv.sma;

import go.Seq;

public abstract class Sma {
    private Sma() {
    }

    public static void touch() {
    }

    private static native void _init();

    public static native String invoke(String var0);

    static {
        Seq.touch();
        _init();
    }
}

From this line more precisely:
Seq.touch();
What's the go.Seq library?

Problem fixed. Here are the Proguard rules:

# Fiskaly
-keepclassmembers enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}
-keep class com.fiskaly.kassensichv.sma.** { *; }
-keep class go.** { *; }