Gst.Caps.prototype.is_always_compatible

function is_always_compatible(caps2:Gst.Caps):Boolean {
    // Gjs wrapper for gst_caps_is_always_compatible()
}

A given Gst.Caps structure is always compatible with another if every media format that is in the first is also contained in the second. That is, caps1 is a subset of caps2.