input: Write a python function to calculate the sum of all odd numbers between two given numbers.
  assert sum_odd_numbers(1, 10) == 25
  assert sum_odd_numbers(5, 15) == 55
  assert sum_odd_numbers(0, 0) == 0
output: def sum_odd_numbers(a, b):
      return sum(x for x in range(a, b+1) if x % 2 != 0)