I'm trying to use the Tri-State-Checkbox library authored by sephiroth74 and am getting an error when I run the application

I followed the installation instructions at android arsenal and was able to build the solution but when I try to run the app I get this error:

2020-02-27 14:49:01.800 14357-14357/com.software.test E/AndroidRuntime: FATAL EXCEPTION: main Process: com.software.test, PID: 14357 java.lang.NoClassDefFoundError: Failed resolution of: Ltimber/log/Timber; at it.sephiroth.android.library.checkbox3state.CheckBox3.(CheckBox3.java:19) at java.lang.reflect.Constructor.newInstance0(Native Method) at java.lang.reflect.Constructor.newInstance(Constructor.java:343) at android.view.LayoutInflater.createView(LayoutInflater.java:852) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:1004) at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:959) at android.view.LayoutInflater.rInflate(LayoutInflater.java:1121) at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:1082) at android.view.LayoutInflater.inflate(LayoutInflater.java:680) at android.view.LayoutInflater.inflate(LayoutInflater.java:532) at android.view.LayoutInflater.inflate(LayoutInflater.java:479) at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:469) at androidx.

I've also tried to follow the installation instructions at his github repository, but I can't even get the solution to build if follow those. So for the time being I've deserted this route.