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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def compare_version(a, b):
 """Compare two version number strings of the form W.X.Y.Z. The numbers are compared most-significant to least-significant. For example, 12.345.67.89 > 2.987.88.99. Args: a: First version number string to compare b: Second version number string to compare Returns: 0 if the numbers are identical, a positive number if 'a' is larger, and a negative number if 'b' is larger. """

  aa = string.split(a, ".")
  bb = string.split(b, ".")
  for i in range(0, 4):
    if aa[i] != bb[i]:
      return cmp(int(aa[i]), int(bb[i]))
  return 0