How to use the elementpath.Selector function in elementpath

def _parse(self):
        super(XsdSelector, self)._parse()
        try:
            self.path = self.elem.attrib['xpath']
        except KeyError:
            self.parse_error("'xpath' attribute required:", self.elem)
            self.path = "*"
        else:
            if not self.pattern.match(self.path.replace(' ', '')):
                self.parse_error("Wrong XPath expression for an xs:selector")

        try:
            self.xpath_selector = Selector(self.path, self.namespaces, parser=XsdIdentityXPathParser)
        except ElementPathError as err:
            self.parse_error(err)
            self.xpath_selector = Selector('*', self.namespaces, parser=XsdIdentityXPathParser)

        # XSD 1.1 xpathDefaultNamespace attribute
        if self.schema.XSD_VERSION > '1.0':
            if 'xpathDefaultNamespace' in self.elem.attrib:
                self.xpath_default_namespace = self._parse_xpath_default_namespace(self.elem)
            else:
                self.xpath_default_namespace = self.schema.xpath_default_namespace

level -= 1
                        if level == 0:
                            yield node
                            node.clear()
                    elif event == 'start-ns':
                        nsmap.append(node)
                        namespaces[node[0]] = node[1]
                    else:
                        try:
                            del namespaces[nsmap.pop()[0]]
                        except KeyError:
                            pass
                        namespaces.update(nsmap)

            else:
                selector = Selector(path, namespaces, strict=False, parser=XmlResourceXPathParser)
                path = path.replace(' ', '').replace('./', '')
                path_level = path.count('/') + 1 if path != '.' else 0
                select_all = '*' in path and set(path).issubset({'*', '/'})

                level = 0
                for event, node in self.iterparse(resource, events):
                    if event == "start":
                        if level == 0:
                            self._root.clear()
                            self._root = node
                        level += 1
                    elif event == 'end':
                        level -= 1
                        if level == path_level and \
                                (select_all or node in selector.select(self._root)):
                            yield node

def _parse(self):
        super(XsdSelector, self)._parse()
        try:
            self.path = self.elem.attrib['xpath']
        except KeyError:
            self.parse_error("'xpath' attribute required:", self.elem)
            self.path = "*"
        else:
            if not self.pattern.match(self.path.replace(' ', '')):
                self.parse_error("Wrong XPath expression for an xs:selector")

        try:
            self.xpath_selector = Selector(self.path, self.namespaces, parser=XsdIdentityXPathParser)
        except ElementPathError as err:
            self.parse_error(err)
            self.xpath_selector = Selector('*', self.namespaces, parser=XsdIdentityXPathParser)

        # XSD 1.1 xpathDefaultNamespace attribute
        if self.schema.XSD_VERSION > '1.0':
            if 'xpathDefaultNamespace' in self.elem.attrib:
                self.xpath_default_namespace = self._parse_xpath_default_namespace(self.elem)
            else:
                self.xpath_default_namespace = self.schema.xpath_default_namespace