Given an object or Element class, return the suitable plotting
        class needed to render it with the current renderer.

def plotting_class(cls, obj):
        """
        Given an object or Element class, return the suitable plotting
        class needed to render it with the current renderer.
        """
        if isinstance(obj, AdjointLayout) or obj is AdjointLayout:
            obj  = Layout
        if isinstance(obj, type):
            element_type = obj
        else:
            element_type = obj.type if isinstance(obj, HoloMap) else type(obj)
        try:
            plotclass = Store.registry[cls.backend][element_type]
        except KeyError:
            raise SkipRendering("No plotting class for {0} "
                                "found".format(element_type.__name__))
        return plotclass