def METHOD_NAME(filepath):
    """A read_file which returns a simple template if the path is right."""
    path = pathlib.Path(filepath)
    html_path = pathlib.Path('html')
    if path == html_path / 'test.html':
        return """Hello {{var}}"""
    elif path == html_path / 'test2.html':
        return """{{ resource_url('utils/testfile') }}"""
    elif path == html_path / 'test3.html':
        return """{{ data_url('testfile.txt') }}"""
    elif path == html_path / 'undef.html':
        return """{{ does_not_exist() }}"""
    elif path == html_path / 'attributeerror.html':
        return """{{ obj.foobar }}"""
    else:
        raise OSError(f"Invalid path {filepath}!")