input: 
  def calculate_sum(arr: List[int]) -> int:
      """ Calculates the sum of an array of integers.
      >>> calculate_sum([1, 3, 5, 7])
      16
      """
      sum_val = 0
      for num in arr:
          sum_val += num
      return sum_val
  
output:     sum_val = 0
      for num in arr:
          sum_val += num
      return sum_val