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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_nbytes(dset):
 """ If the dataset has an attribute 'nbytes', return it. Otherwise get the size of the underlying array. Returns None if the dataset is actually a group. """

    if 'nbytes' in dset.attrs:
        # look if the dataset has an attribute nbytes
        return dset.attrs['nbytes']
    elif hasattr(dset, 'dtype'):
        # else extract nbytes from the underlying array
        return dset.size * numpy.zeros(1, dset.dtype).nbytes