def _tuplify(obj):
    if np.iterable(obj) and not isinstance(obj, string_types):
        res = tuple(str(o) for o in obj)
    else:
        res = (str(obj),)
    return res
convert an object in a tuple of strings (even if it is not iterable,
dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/graphics/mosaicplot.py/_tuplify