code: def real_cepstrum(x, n=None):
      """
      Compute the real cepstrum of a real sequence.
      x : ndarray
          Real sequence to compute real cepstrum of.
      n : {None, int}, optional
          Length of the Fourier transform.
      Returns
      -------
      ceps: ndarray
          The real cepstrum.
      """
      spectrum = numpy.fft.fft(x, n=n)
      ceps = numpy.fft.ifft(numpy.log(numpy.abs(spectrum))).real
  
      return ceps
  
file_path: cupy/tests/cupyx_tests/signal_tests/acoustics_tests/test_cepstrum.py
imports: import pytest
  import numpy
  import cupy
  from cupy import testing
  import cupyx.signal
label_desc: Use image node_id 2 for calling a global function with example usage: real_cepstrum(x, n) and returns: ceps