input: 
  def sum_list(list):
      """
      Calculate the sum of all elements in a given list.
  
      >>> sum_list([1, 2, 3])
      6
      >>> sum_list([0, -1, 1])
      0
      """
      sum_value = 0
      for num in list:
          sum_value += num
      return sum_value
  
output:     sum_value = 0
      for num in list:
          sum_value += num
      return sum_value