input: Write a function to calculate the total sum of all elements in a given list. The function should return the sum of the elements in the list. If the list is empty, the function should return 0.
  def calculate_sum_of_list(arr):
      total_sum = 0
      for item in arr:
          total_sum += item
      return total_sum
  
  assert calculate_sum_of_list([1, 2, 3, 4]) == 10
  assert calculate_sum_of_list([5, 10, 15, 20]) == 50
  assert calculate_sum_of_list([0, 0, 0, 0]) == 0
  assert calculate_sum_of_list([-1, -2, -3, -4]) == -10
  assert calculate_sum_of_list([]) == 0
output: def calculate_sum_of_list(arr):
      total_sum = 0
      for item in arr:
          total_sum += item
      return total_sum