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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 _normalize_overlap(overlap, window, nfft, samp, method='welch'):
 """Normalise an overlap in physical units to a number of samples Parameters overlap : `float`, `Quantity`, `None` the overlap in some physical unit (seconds) window : `str` the name of the window function that will be used, only used if `overlap=None` is given nfft : `int` the number of samples that will be used in the fast Fourier transform samp : `Quantity` the sampling rate (Hz) of the data that will be transformed method : `str` the name of the averaging method, default: `'welch'`, only used to return `0` for `'bartlett'` averaging Returns ------- noverlap : `int` the number of samples to be be used for the overlap """

    if method == 'bartlett':
        return 0
    if overlap is None and isinstance(window, string_types):
        return recommended_overlap(window, nfft)
    if overlap is None:
        return 0
    return seconds_to_samples(overlap, samp)