input: Write a function called sum_list that takes a list of numbers as input and returns the sum of all the numbers in the list.
  
  assert sum_list([1, 2, 3, 4]) == 10
  assert sum_list([0, -1, 1]) == 0
  assert sum_list([5]) == 5
  assert sum_list([]) == 0
  assert sum_list([-1, -2, -3]) == -6
output: def sum_list(numbers):
      return sum(numbers)