input: Write a python function to determine the maximum of two values without using the max function.
  assert max_of_two(7, 3) == 7
  assert max_of_two(10, 20) == 20
  assert max_of_two(5, 5) == 5
output: def max_of_two(a, b):
      if a > b:
          return a
      else:
          return b