input: from typing import List
  
  def calculate_sum(arr: List[int]) -> int:
      """ Calculate the sum of elements in a given list of integers.
      >>> calculate_sum([1, 3, 5, 7])
      16
      >>> calculate_sum([2, 4, 6, 8])
      20
      """
output:     total = 0
      for num in arr:
          total += num
      return total