code: def spectrogram(self, stride, fftlength=None, overlap=None, window='hann',
                      method=DEFAULT_FFT_METHOD, nproc=1, **kwargs):
          
          # get method
          method_func = spectral.get_method(method)
  
          # calculate PSD using UI method
          return spectral.average_spectrogram(
              self,
              method_func,
              stride,
              fftlength=fftlength,
              overlap=overlap,
              window=window,
              **kwargs
          )
docs: Calculate the average power spectrogram of this `TimeSeries`
          using the specified average spectrum method.
  
          Each time-bin of the output `Spectrogram` is calculated by taking
          a chunk of the `TimeSeries` in the segment
          `[t - overlap/2., t + stride + overlap/2.)` and calculating the
          :meth:`~gwpy.timeseries.TimeSeries.psd` of those data.
  
          As a result, each time-bin is calculated using `stride + overlap`
          seconds of data.
  
          Parameters
          ----------
          stride : `float`
              number of seconds in single PSD (column of spectrogram).
  
          fftlength : `float`
              number of seconds in single FFT.
  
          overlap : `float`, optional
              number of seconds of overlap between FFTs, defaults to the
              recommended overlap for the given window (if given), or 0
  
          window : `str`, `numpy.ndarray`, optional
              window function to apply to timeseries prior to FFT,
              see :func:`scipy.signal.get_window` for details on acceptable
              formats
  
          method : `str`, optional
              FFT-averaging method, see *Notes* for more details
  
          nproc : `int`
              number of CPUs to use in parallel processing of FFTs
  
          Returns
          -------
          spectrogram : `~gwpy.spectrogram.Spectrogram`
              time-frequency power spectrogram as generated from the
              input time-series.
  
          Notes
          -----
          The accepted ``method`` arguments are:
  
          - ``'bartlett'`` : a mean average of non-overlapping periodograms
          - ``'median'`` : a median average of overlapping periodograms
          - ``'welch'`` : a mean average of overlapping periodograms