input: Write a python function to find the average of a list of numbers.
  assert avg_list([1, 3, 5, 3, 7, 1]) == 3.3333333333333335
  assert avg_list([10, 20, 30, 40, 50]) == 30.0
  assert avg_list([2, 4, 6, 8, 10]) == 6.0
output: def avg_list(numbers):
      return sum(numbers) / len(numbers)