Popup, reasons why methods addClass/ removeClass are not returning the popup instance

[ferdicus]

I've noticed, that some Popup methods do return the instance, while others don't (like addClass for example).

Is there a specific rationale behind this, or is it simply an omission?

This makes chaining of methods possible in this way

      new Popup({
        closeButton: false,
        closeOnClick: false,
        anchor: 'bottom',
      })
        .setLngLat([myLng, myLat])
        .setHTML('<div>foobar</div>')
        .addTo(map)
        .addClassName('my-class');

but not in this way

      new Popup({
        closeButton: false,
        closeOnClick: false,
        anchor: 'bottom',
      })
        .setLngLat([myLng, myLat])
        .addClassName('my-class')
        .setHTML('<div>foobar</div>')
        .addTo(map);

thanks in advance

[HarelM]

Probably a mistake, feel free to open a PR.