Parse a textgroup resource

        :param resource: Element representing the textgroup
        :param parent: Parent of the textgroup
        :param _cls_dict: Dictionary of classes to generate subclasses

def parse(cls, resource, parent=None):
        """ Parse a textgroup resource

        :param resource: Element representing the textgroup
        :param parent: Parent of the textgroup
        :param _cls_dict: Dictionary of classes to generate subclasses
        """
        xml = xmlparser(resource)
        o = cls(urn=xml.get("urn"), parent=parent)

        for child in xml.xpath("ti:groupname", namespaces=XPATH_NAMESPACES):
            lg = child.get("{http://www.w3.org/XML/1998/namespace}lang")
            if lg is not None:
                o.set_cts_property("groupname", child.text, lg)

        # Parse Works
        _xpathDict(xml=xml, xpath='ti:work', cls=cls.CLASS_WORK, parent=o)

        _parse_structured_metadata(o, xml)
        return o