input: Write a function to calculate the total sum of all elements in a given list. The function should take a list as input and return the sum of its elements. If the list is empty, the function should return 0.
  assert calculate_total_sum([1, 9, 3, 5])==18
  assert calculate_total_sum([-1, -2, 3])==0
  assert calculate_total_sum([])==0
output: def calculate_total_sum(lst):
      return sum(lst) if lst else 0