def _prop_descriptions(self):
        return """\
        color

        family
            HTML font family - the typeface that will be applied by
            the web browser. The web browser will only be able to
            apply a font if it is available on the system which it
            operates. Provide multiple font families, separated by
            commas, to indicate the preference in which to apply
            fonts if they aren't available on the system. The Chart
            Studio Cloud (at https://chart-studio.plotly.com or on-
            premise) generates images on a server, where only a
            select number of fonts are installed and supported.
            These include "Arial", "Balto", "Courier New", "Droid
            Sans",, "Droid Serif", "Droid Sans Mono", "Gravitas
            One", "Old Standard TT", "Open Sans", "Overpass", "PT
            Sans Narrow", "Raleway", "Times New Roman".
        size

        """