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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_field(self, field):
 """Return the dataset corresponds to the provided key. Example:: a = np.ones((2,2)) b = np.zeros((2,2)) np.savez('data.npz', a=a, b=b) dataset = NumpyDataset('data.npz') data_a = dataset.get_field('a') data_b = dataset.get_field('b') Parameters field : str The name of the field to retrieve. """

        idx = self._keys.index(field)
        return self._data[idx]