'Registers a :class:`~horizon.Panel` with this dashboard.'

@classmethod
def register(cls, panel):

    panel_class = Horizon.register_panel(cls, panel)
    panel_mod = import_module(panel.__module__)
    panel_dir = os.path.dirname(panel_mod.__file__)
    template_dir = os.path.join(panel_dir, 'templates')
    if os.path.exists(template_dir):
        key = os.path.join(cls.slug, panel.slug)
        loaders.panel_template_dirs[key] = template_dir
    return panel_class
