"Element sh.siava.rangesliderpreference.RangeSliderPreference is not allowed here" in Preferences Screen

[adrian-best]

Hello,

Running on Android Studio Dolphin | 2021.3.1 Patch 1, *working in Kotlin and XML.

In Terminal, I ran "git submodule add https://github.com/siavash79/rangesliderpreference" and "git submodule update --init --recursive". I can see the submodule when write "git submodule status"

I then tried inputting the example code into my preferences screen, but I am getting this error:
"Element sh.siava.rangesliderpreference.RangeSliderPreference is not allowed here"

<SwitchPreferenceCompat
    app:key="notifications"
    app:title="Enable message notifications"/>



<Preference
    app:key="feedback"
    app:title="Send feedback"
    app:summary="Report technical issues or suggest new features"/>

<sh.siava.rangesliderpreference.RangeSliderPreference
    android:key="MY_KEY"
    android:title="Range Slider"
    android:summary="Set the default values for the percentages when adding a new RIR"
    app:tickInterval="5"
    app:valueCount="2"
    app:minVal="0"
    app:maxVal="100"
    app:defaultValue="20,50"
    />