input: Write a python function to calculate the sum of all numbers in a list.
  assert sum_list([7, 15, 23, 5, 9]) == 59
  assert sum_list([1, 2, 3, 4, 5]) == 15
  assert sum_list([-1, -2, -3, -4, -5]) == -15
output: def sum_list(numbers):
      return sum(numbers)