How to use the cget.util.ls function in cget

def _list_files(self, pkg=None, top=True):
        if pkg is None:
            return util.ls(self.get_package_directory(), os.path.isdir)
        else:
            p = self.parse_pkg_src(pkg)
            ls = util.ls(self.get_deps_directory(p.to_fname()), os.path.isfile)
            if top: return [p.to_fname()]+list(ls)
            else: return ls

def size_command(prefix, n):
    pkgs = len(list(util.ls(prefix.get_package_directory(), os.path.isdir)))
    if pkgs != int(n):
        raise util.BuildError("Not the correct number of items: {}".format(pkgs))

def _list_files(self, pkg=None, top=True):
        if pkg is None:
            return util.ls(self.get_package_directory(), os.path.isdir)
        else:
            p = self.parse_pkg_src(pkg)
            ls = util.ls(self.get_deps_directory(p.to_fname()), os.path.isfile)
            if top: return [p.to_fname()]+list(ls)
            else: return ls

def link(self, pkg):
        pkg = self.parse_pkg_src(pkg)
        pkg_dir = self.get_package_directory(pkg.to_fname())
        unlink_dir = self.get_unlink_directory(pkg.to_fname())
        if os.path.exists(unlink_dir):
            os.rename(unlink_dir, pkg_dir)
            if util.USE_SYMLINKS: util.symlink_dir(os.path.join(pkg_dir, 'install'), self.prefix)
            else: util.copy_dir(os.path.join(pkg_dir, 'install'), self.prefix)
        # Relink dependencies
        for dep in util.ls(self.get_unlink_directory(), os.path.isdir):
            ls = util.ls(self.get_unlink_deps_directory(dep), os.path.isfile)
            if pkg.to_fname() in ls: self.link(dep)

def link(self, pkg):
        pkg = self.parse_pkg_src(pkg)
        pkg_dir = self.get_package_directory(pkg.to_fname())
        unlink_dir = self.get_unlink_directory(pkg.to_fname())
        if os.path.exists(unlink_dir):
            os.rename(unlink_dir, pkg_dir)
            if util.USE_SYMLINKS: util.symlink_dir(os.path.join(pkg_dir, 'install'), self.prefix)
            else: util.copy_dir(os.path.join(pkg_dir, 'install'), self.prefix)
        # Relink dependencies
        for dep in util.ls(self.get_unlink_directory(), os.path.isdir):
            ls = util.ls(self.get_unlink_deps_directory(dep), os.path.isfile)
            if pkg.to_fname() in ls: self.link(dep)