input: Write a function to calculate the total sum of all elements in the given list using a for loop.
  assert calculate_sum([1, 9, 3, 5])==18
  assert calculate_sum([2, 4, 6, 8])==20
  assert calculate_sum([])==0
output: def calculate_sum(lst):
      total = 0
      for num in lst:
          total += num
      return total