input: def sum_list(input_list):
      """
      Calculate the sum of the items in the given list.
  
      >>> sum_list([1, 2, 3, 4])
      10
      >>> sum_list([-1, -2, 3, 4])
      4
      >>> sum_list([])
      0
      """
      pass
output:     total = 0
      for num in input_list:
          total += num
      return total