def METHOD_NAME():
    """
    Return the string representing the configuration dir.
    The default is set by "AppDirs" and can be accessed by importing
    ``sunpy.util.config.CONFIG_DIR``. You can override this with the
    "SUNPY_CONFIGDIR" environment variable.
    """
    configdir = os.environ.get('SUNPY_CONFIGDIR', CONFIG_DIR)
    if not _is_writable_dir(configdir):
        raise RuntimeError(f'Could not write to SUNPY_CONFIGDIR="{configdir}"')
    return configdir