input: Write a function to calculate the sum of a list of integers. The function should return the total sum of the elements in the list. If the list is empty, the function should return 0.
  
  assert sum_list([1, 2, 3, 4, 5]) == 15
  assert sum_list([10, 20, 30]) == 60
  assert sum_list([0, -1, 1]) == 0
  assert sum_list([]) == 0
output: def sum_list(lst):
      return sum(lst) if lst else 0