code: def max_contrast(array):
      """Sets all positive values to one and all negative values to -1.
  
      Needed for first pass lookup on word table.
  
      Args:
          array (numpy.ndarray): target array
      """
      array[array > 0] = 1
      array[array < 0] = -1
  
      return None
  
file_path: image-match/image_match/signature_database_base.py
imports: from image_match.goldberg import ImageSignature
  from itertools import product
  from operator import itemgetter
  import numpy
label_desc: Use image node_id 4 for calling a global function with example usage: max_contrast(array) and returns: None