How to use the essentia.standard.Spectrum function in essentia

def create_analyzers(fs=44100.0,
                     nhop=512,
                     nffts=[1024, 2048, 4096],
                     mel_nband=80,
                     mel_freqlo=27.5,
                     mel_freqhi=16000.0):
    analyzers = []
    for nfft in nffts:
        window = Windowing(size=nfft, type='blackmanharris62')
        spectrum = Spectrum(size=nfft)
        mel = MelBands(inputSize=(nfft // 2) + 1,
                       numberBands=mel_nband,
                       lowFrequencyBound=mel_freqlo,
                       highFrequencyBound=mel_freqhi,
                       sampleRate=fs)
        analyzers.append((window, spectrum, mel))
    return analyzers

numBins : (integer ∈ [12, ∞), default = 12) :
            the size of the output HPCP (must be a positive nonzero multiple of 12)
            whitening : (boolean (True, False), default = False)
            Optional step of computing spectral whitening to the output from speakPeak magnitudes
        '''

        audio = array(self.audio_vector)

        #print audio.shape

        frameGenerator = estd.FrameGenerator(audio, frameSize=frameSize, hopSize=hopSize)

        window = estd.Windowing(type=windowType)

        spectrum = estd.Spectrum()

        # Refer http://essentia.upf.edu/documentation/reference/std_SpectralPeaks.html
        spectralPeaks = estd.SpectralPeaks(magnitudeThreshold=0,
                                            maxFrequency=maxFrequency,
                                            minFrequency=minFrequency,
                                            maxPeaks=maxPeaks,
                                            orderBy="frequency",
                                            sampleRate=self.fs)

        # http://essentia.upf.edu/documentation/reference/std_SpectralWhitening.html
        spectralWhitening = estd.SpectralWhitening(maxFrequency= maxFrequency,
                                                    sampleRate=self.fs)

        # http://essentia.upf.edu/documentation/reference/std_HPCP.html
        hpcp = estd.HPCP(sampleRate=self.fs,
                        maxFrequency=maxFrequency,

"""
    Wrap around the essentia library to compute HPCP features
    :param XAudio: A flat array of raw audio samples
    :param Fs: Sample rate
    :param winSize: Window size of each STFT window
    :param hopSize: Hop size between STFT windows
    :param squareRoot: Do square root compression?
    :param NChromaBins: How many chroma bins (default 36)
    :returns H: An (NChromaBins x NWindows) matrix of all
        chroma windows
    """
    import essentia
    from essentia import Pool, array
    import essentia.standard as ess
    print("Getting HPCP Essentia...")
    spectrum = ess.Spectrum()
    window = ess.Windowing(size=winSize, type='hann')
    spectralPeaks = ess.SpectralPeaks()
    hpcp = ess.HPCP(size = NChromaBins)
    H = []
    for frame in ess.FrameGenerator(XAudio, frameSize=winSize, hopSize=hopSize, startFromZero = True):
        S = spectrum(window(frame))
        freqs, mags = spectralPeaks(S)
        H.append(hpcp(freqs, mags))
    H = np.array(H)
    H = H.T
    if squareRoot:
        H = sqrtCompress(H)
    return H

def __init__(self, frame_size, hop_size, window_type, feature,
            beats, sample_rate):
        """STFTFeature constructor."""
        self.frame_size = frame_size
        self.hop_size = hop_size
        self.window_type = window_type
        self.w = ES.Windowing(type=window_type)
        self.spectrum = ES.Spectrum()
        self.feature = feature  # Essentia feature object
        self.beats = beats
        self.sample_rate = sample_rate

def __init__(self, frame_size, hop_size, window_type, feature, sample_rate,
                 beats=None):
        """STFTFeature constructor."""
        self.frame_size = frame_size
        self.hop_size = hop_size
        self.window_type = window_type
        self.w = ES.Windowing(type=window_type)
        self.spectrum = ES.Spectrum()
        self.feature = feature  # Essentia feature object
        self.beats = beats
        self.sample_rate = sample_rate