input: Write a function to calculate the total sum of all elements in a given list.
  assert calculate_sum([1, 9, 3, 5])==18
  assert calculate_sum([])==0
  assert calculate_sum([-1, -9, -3, -5])==-18
  assert calculate_sum([4, 4, 4, 4])==16
output: def calculate_sum(lst):
      return sum(lst)