How to use the nitpick.generic.is_url function in nitpick

def fetch_style_from_url(self, url: str) -> Optional[Path]:
        """Fetch a style file from a URL, saving the contents in the cache dir."""
        if NitpickApp.current().offline:
            # No style will be fetched in offline mode
            return None

        if self._first_full_path and not is_url(url):
            prefix, rest = self._first_full_path.split(":/")
            domain_plus_url = str(rest).strip("/").rstrip("/") + "/" + url
            new_url = "{}://{}".format(prefix, domain_plus_url)
        else:
            new_url = url

        parsed_url = list(urlparse(new_url))
        if not parsed_url[2].endswith(TOML_EXTENSION):
            parsed_url[2] += TOML_EXTENSION
        new_url = urlunparse(parsed_url)

        if new_url in self._already_included:
            return None

        if not NitpickApp.current().cache_dir:
            raise FileNotFoundError("Cache dir does not exist")

def get_style_path(self, style_uri: str) -> Optional[Path]:
        """Get the style path from the URI. Add the .toml extension if it's missing."""
        clean_style_uri = style_uri.strip()

        style_path = None
        if is_url(clean_style_uri) or is_url(self._first_full_path):
            style_path = self.fetch_style_from_url(clean_style_uri)
        elif clean_style_uri:
            style_path = self.fetch_style_from_local_path(clean_style_uri)
        return style_path