code: def fft_frequencies(num_fft_bins, sample_rate):
      """
      Frequencies of the FFT bins.
  
      Parameters
      ----------
      num_fft_bins : int
          Number of FFT bins (i.e. half the FFT length).
      sample_rate : float
          Sample rate of the signal.
  
      Returns
      -------
      fft_frequencies : numpy array
          Frequencies of the FFT bins [Hz].
  
      """
      return np.fft.fftfreq(num_fft_bins * 2, 1.0 / sample_rate)[
          :num_fft_bins
      ]
  
imports: from __future__ import absolute_import, division, print_function
  import warnings
  import numpy
  import scipy.fftpack
  from ..processors import Processor
  from .signal import Signal, FramedSignal
label_desc: Use image node_id 1 for calling a global function with example usage: fft_frequencies(num_fft_bins, sample_rate) and returns: np