code: def dc_normalize(sig_array):
      """Removes DC and normalizes to -1, 1 range"""
      sig_array_norm = sig_array.copy()
      sig_array_norm -= sig_array_norm.mean()
      sig_array_norm /= abs(sig_array_norm).max() + 1e-10
      return sig_array_norm
  
imports: from __future__ import print_function
  import math
  import numpy
  import sys
  from scipy.fftpack import fft
  import matplotlib.pyplot
  from scipy.signal import lfilter
  from scipy.fftpack.realtransforms import dct
  from tqdm import tqdm
label_desc: Use image node_id 1 for calling a global function with example usage: dc_normalize(sig_array) and returns: sig_array_norm