How to use the svglib.svglib.ElementWrapper.apply_rules function in svglib

"""Search an attribute with some name in some node or above.

        First the node is searched, then its style attribute, then
        the search continues in the node's parent node. If no such
        attribute is found, '' is returned.
        """

        # This needs also to lookup values like "url(#SomeName)"...

        if not svgNode.attrib.get('__rules_applied', False):
            # Apply global styles...
            if self.css_rules is not None:
                if isinstance(svgNode, NodeTracker):
                    svgNode.apply_rules(self.css_rules)
                else:
                    ElementWrapper(svgNode).apply_rules(self.css_rules)
            # ...and locally defined
            if svgNode.attrib.get("style"):
                attrs = self.parseMultiAttributes(svgNode.attrib.get("style"))
                for key, val in attrs.items():
                    # lxml nodes cannot accept attributes starting with '-'
                    if not key.startswith('-'):
                        svgNode.attrib[key] = val
                svgNode.attrib['__rules_applied'] = '1'

        attr_value = svgNode.attrib.get(name, '').strip()

        if attr_value and attr_value != "inherit":
            return attr_value
        if svgNode.getparent() is not None:
            return self.findAttr(svgNode.getparent(), name)
        return ''