def METHOD_NAME(d):
    """
    Convert nested dictionary to flat map,
    """
    def items():
        for key, value in list(d.items()):
            if isinstance(value, dict):
                for subkey, subvalue in list(METHOD_NAME(value).items()):
                    yield key + "." + subkey, subvalue
            else:
                yield key, value
    return dict(items())