input: Write a function to print the absolute difference between two given numbers. If the given numbers are A and B, the function should return |A - B|. If the given numbers are empty then return 0.
  
  assert absolute_difference(9, 5)==4
  assert absolute_difference(-1, -5)==4
  assert absolute_difference(0, 0)==0
  assert absolute_difference(7, 10)==3
  assert absolute_difference(0, -9)==9
output: def absolute_difference(A=None, B=None):
      if A is None or B is None:
          return 0
      return abs(A - B)