input: def sum_list(lst):
      """
      This function takes a list of numbers and returns the sum of all elements in the list.
      
      >>> sum_list([1, 2, 3, 4, 5])
      15
      >>> sum_list([0, 0, 0, 0, 0])
      0
      >>> sum_list([-1, -2, -3, -4, -5])
      -15
      """
output:     total = 0
      for num in lst:
          total += num
      return total