app/src/main/res/values/attrs.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="CascadeLayout">
        <attr name="horizontal_spacing" format="dimension" />
        <attr name="vertical_spacing" format="dimension" />
    </declare-styleable>

    <declare-styleable name="CascadeLayout_LayoutParams">
        <attr name="layout_vertical_spacing" format="dimension" />
    </declare-styleable>
</resources>