def __len__(self):
        raise NotImplementedError('len(obj) needs implementing.')
Returns a ( width, height ) tuple containing the size of a
dataset/ETHPy150Open ntoll/p4p2p/p4p2p/dht/storage.py/DataStore.__len__--crossover with--dataset/ETHPy150Open enthought/traitsui/traitsui/qt4/toolkit.py/GUIToolkit.image_size