input: Write a function to calculate the total sum of all elements in a given list using a for loop. If the list is empty, return 0.
  
  assert calculate_sum([1, 9, 3, 5]) == 18
  assert calculate_sum([]) == 0
  assert calculate_sum([7, 2, 9, 1, 5]) == 24
  assert calculate_sum([10, -3, 4, 2]) == 13
  assert calculate_sum([5]) == 5
output: def calculate_sum(lst):
      total = 0
      for num in lst:
          total += num
      return total