code: def fft_freqs(n_fft, fs):
      
      return np.arange(0, (n_fft // 2 + 1)) / float(n_fft) * float(fs)
docs: Return frequencies for DFT
  
      Parameters
      ----------
      n_fft : int
          Number of points in the FFT.
      fs : float
          The sampling rate.