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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 butter_filter(cutoff, fs, order=5, btype='low'):
    '''Create a digital butter fileter with cutoff frequency in Hz

    Args
    ----
    cutoff: float
        Cutoff frequency where filter should separate signals
    fs: float
        sampling frequency
    btype: str
        Type of filter type to create. 'low' creates a low-frequency filter and
        'high' creates a high-frequency filter (Default 'low).

    Returns
    -------
    b: ndarray
        Numerator polynomials of the IIR butter filter
    a: ndarray
        Denominator polynomials of the IIR butter filter

    Notes
    -----
    This function was adapted from the following StackOverflow answer:
    http://stackoverflow.com/a/25192640/943773
    '''
    import scipy.signal

    nyq = 0.5 * fs
    normal_cutoff = cutoff / nyq
    b, a = scipy.signal.butter(order, normal_cutoff, btype=btype, analog=False)

    return b, a