def add_styles(self):
        """Add the css to the svg"""
        colors = self.graph.style.get_colors(self.id, self.graph._order)
        strokes = self.get_strokes()
        all_css = []
        auto_css = ['file://base.css']

        if self.graph.style._google_fonts:
            auto_css.append(
                '//fonts.googleapis.com/css?family=%s' %
                quote_plus('|'.join(self.graph.style._google_fonts))
            )

        for css in auto_css + list(self.graph.css):
            css_text = None
            if css.startswith('inline:'):
                css_text = css[len('inline:'):]
            elif css.startswith('file://'):
                css = css[len('file://'):]

                if not os.path.exists(css):
                    css = os.path.join(os.path.dirname(__file__), 'css', css)

                with io.open(css, encoding='utf-8') as f:
                    css_text = template(
                        f.read(),
                        style=self.graph.style,
                        colors=colors,
                        strokes=strokes,
                        id=self.id
                    )

            if css_text is not None:
                if not self.graph.pretty_print:
                    css_text = minify_css(css_text)
                all_css.append(css_text)
            else:
                if css.startswith('//') and self.graph.force_uri_protocol:
                    css = '%s:%s' % (self.graph.force_uri_protocol, css)
                self.processing_instructions.append(
                    etree.PI(u('xml-stylesheet'), u('href="%s"' % css))
                )
        self.node(
            self.defs, 'style', type='text/css'
        ).text = '\n'.join(all_css)
Add the css to the svg