input: Write a function that takes a list of integers and returns the sum of the elements. The function should return the sum as an integer. If the list is empty, the function should return 0.
  
  def sum_list(lst):
    total = 0
    for num in lst:
      total += num
    return total
  
  assert sum_list([1, 2, 3, 4, 5]) == 15
  assert sum_list([]) == 0
  assert sum_list([-1, 0, 1]) == 0
  assert sum_list([10, 20, 30, 40, 50]) == 150
output: def sum_list(lst):
    total = 0
    for num in lst:
      total += num
    return total