input: Write a function to calculate the sum of the items in a given list.
  
  assert sum_list([1, 2, 3, 4, 5])==15
  assert sum_list([0, 0, 0])==0
  assert sum_list([-1, 1, -1, 1])==0
  assert sum_list([10, 20, 30, 40])==100
  assert sum_list([])==0
output: def sum_list(lst):
      return sum(lst)