krita-plugins/image_fitter_docker/__init__.py

from krita import DockWidgetFactory, DockWidgetFactoryBase
from .image_fitter_docker import ImageFitter

DOCKER_ID = 'image_fitter'
instance = Krita.instance()
dock_widget_factory = DockWidgetFactory(DOCKER_ID,
                                        DockWidgetFactoryBase.DockRight,
                                        ImageFitter)

instance.addDockWidgetFactory(dock_widget_factory)