=====
            Key       Value Default Description
            ========= ===== ======= =========================================
            facecolor color 'white' The facecolor of the slider handles.
            edgecolor color '.75'   The edgecolor of the slider handles.
            size      int   10      The size of the slider handles in points.
            ========= ===== ======= =========================================

            Other values will be transformed as marker{foo} and passed to the
            `~.Line2D` constructor. e.g. ``handle_style = {'style'='x'}`` will
            result in ``markerstyle = 'x'``.

        Notes
        -----
        Additional kwargs are passed on to ``self.poly`` which is the
        `~matplotlib.patches.Polygon` that draws the slider knob.  See the
        `.Polygon` documentation for valid property names (``facecolor``,
        ``edgecolor``, ``alpha``, etc.).
        Nr