How to use the emmett.ctx.current.app function in emmett

def http(
        self, path, args=[], params={}, anchor=None,
        sign=None, scheme=None, host=None, language=None
    ):
        if not isinstance(args, (list, tuple)):
            args = [args]
        # allow user to use url('static', 'file')
        if path == 'static':
            path = '/static'
        # routes urls with 'dot' notation
        if '/' not in path:
            # urls like 'function' refers to same module
            if '.' not in path:
                namespace = current.app.config.url_default_namespace or \
                    current.app.name
                path = namespace + "." + path
            # urls like '.function' refers to main app module
            elif path.startswith('.'):
                if not hasattr(current, 'request'):
                    raise RuntimeError(
                        f'cannot build url("{path}",...) '
                        'without current request'
                    )
                module = current.request.name.rsplit('.', 1)[0]
                path = module + path
            # find correct route
            try:
                url_components = \
                    current.app._router_http.routes_out[path]['path']
                url_host = current.app._router_http.routes_out[path]['host']
                builder = HttpUrlBuilder(url_components)

current.app.name
                path = namespace + "." + path
            # urls like '.function' refers to main app module
            elif path.startswith('.'):
                if not hasattr(current, 'request'):
                    raise RuntimeError(
                        f'cannot build url("{path}",...) '
                        'without current request'
                    )
                module = current.request.name.rsplit('.', 1)[0]
                path = module + path
            # find correct route
            try:
                url_components = \
                    current.app._router_ws.routes_out[path]['path']
                url_host = current.app._router_ws.routes_out[path]['host']
                builder = UrlBuilder(url_components)
                # try to use the correct hostname
                if url_host is not None:
                    # TODO: remap host
                    try:
                        if current.request.host != url_host:
                            scheme = \
                                self.http_to_ws_schemes[current.request.scheme]
                            host = url_host
                    except Exception:
                        pass
            except KeyError:
                raise RuntimeError(f'invalid url("{path}",...)')
        # handle classic urls
        else:
            builder = UrlBuilder([path])

def ws(
        self, path, args=[], params={}, scheme=None, host=None, language=None
    ):
        if not isinstance(args, (list, tuple)):
            args = [args]
        # routes urls with 'dot' notation
        if '/' not in path:
            # urls like 'function' refers to same module
            if '.' not in path:
                namespace = current.app.config.url_default_namespace or \
                    current.app.name
                path = namespace + "." + path
            # urls like '.function' refers to main app module
            elif path.startswith('.'):
                if not hasattr(current, 'request'):
                    raise RuntimeError(
                        f'cannot build url("{path}",...) '
                        'without current request'
                    )
                module = current.request.name.rsplit('.', 1)[0]
                path = module + path
            # find correct route
            try:
                url_components = \
                    current.app._router_ws.routes_out[path]['path']
                url_host = current.app._router_ws.routes_out[path]['host']

namespace = current.app.config.url_default_namespace or \
                    current.app.name
                path = namespace + "." + path
            # urls like '.function' refers to main app module
            elif path.startswith('.'):
                if not hasattr(current, 'request'):
                    raise RuntimeError(
                        f'cannot build url("{path}",...) '
                        'without current request'
                    )
                module = current.request.name.rsplit('.', 1)[0]
                path = module + path
            # find correct route
            try:
                url_components = \
                    current.app._router_http.routes_out[path]['path']
                url_host = current.app._router_http.routes_out[path]['host']
                builder = HttpUrlBuilder(url_components)
                # try to use the correct hostname
                if url_host is not None:
                    try:
                        if current.request.host != url_host:
                            scheme = current.request.scheme
                            host = url_host
                    except Exception:
                        pass
            except KeyError:
                raise RuntimeError(f'invalid url("{path}",...)')
        # handle classic urls
        else:
            builder = HttpUrlBuilder([path])
        # add language

self._logger = None
        self.logger_name = self.import_name
        #: init extensions
        self.ext = sdict()
        self._extensions_env = sdict()
        self._extensions_listeners = {key: [] for key in Extension._signals_}
        #: init templater
        self.templater = Templater(
            path=self.template_path,
            encoding=self.config.templates_encoding,
            escape=self.config.templates_escape,
            prettify=self.config.templates_prettify,
            reload=self.config.templates_auto_reload
        )
        #: store app in current
        current.app = self

def add_prefix(self, args):
        if current.app._router_http._prefix_main:
            self.components.insert(0, '{}')
            args.insert(0, current.app._router_http._prefix_main)

# try to use the correct hostname
                if url_host is not None:
                    try:
                        if current.request.host != url_host:
                            scheme = current.request.scheme
                            host = url_host
                    except Exception:
                        pass
            except KeyError:
                raise RuntimeError(f'invalid url("{path}",...)')
        # handle classic urls
        else:
            builder = HttpUrlBuilder([path])
        # add language
        lang = None
        if current.app.language_force_on_url:
            if language:
                #: use the given language if is enabled in application
                if language in current.app.languages:
                    lang = language
            else:
                #: try to use the request language if context exists
                if hasattr(current, 'request'):
                    lang = current.request.language
            if lang == current.app.language_default:
                lang = None
        # # add extension (useless??)
        # if extension:
        #     url = url + '.' + extension
        # scheme=True means to use current scheme
        if scheme is True:
            if not hasattr(current, 'request'):

raise RuntimeError(f'invalid url("{path}",...)')
        # handle classic urls
        else:
            builder = HttpUrlBuilder([path])
        # add language
        lang = None
        if current.app.language_force_on_url:
            if language:
                #: use the given language if is enabled in application
                if language in current.app.languages:
                    lang = language
            else:
                #: try to use the request language if context exists
                if hasattr(current, 'request'):
                    lang = current.request.language
            if lang == current.app.language_default:
                lang = None
        # # add extension (useless??)
        # if extension:
        #     url = url + '.' + extension
        # scheme=True means to use current scheme
        if scheme is True:
            if not hasattr(current, 'request'):
                raise RuntimeError(
                    f'cannot build url("{path}",...) without current request'
                )
            scheme = current.request.scheme
        # add scheme and host
        if scheme:
            if host is None:
                if not hasattr(current, 'request'):
                    raise RuntimeError(

scheme = \
                                self.http_to_ws_schemes[current.request.scheme]
                            host = url_host
                    except Exception:
                        pass
            except KeyError:
                raise RuntimeError(f'invalid url("{path}",...)')
        # handle classic urls
        else:
            builder = UrlBuilder([path])
        # add language
        lang = None
        if current.app.language_force_on_url:
            if language:
                #: use the given language if is enabled in application
                if language in current.app.languages:
                    lang = language
            else:
                #: try to use the request language if context exists
                if hasattr(current, 'request'):
                    lang = current.request.language
            if lang == current.app.language_default:
                lang = None
        # scheme=True means to use current scheme
        if scheme is True:
            if not hasattr(current, 'request'):
                raise RuntimeError(
                    f'cannot build url("{path}",...) without current request'
                )
            scheme = self.http_to_ws_schemes[current.request.scheme]
        # add scheme and host
        if scheme:

def process(self, ctx, value):
        for helper in self.helpers:
            ctx.html(helper.format(current.app._router_http._prefix_main))