input: Write a function to sort a list of numbers using selection sort. Return the sorted list.
  assert sort_list([4, 2, 6, 7, 1])==[1, 2, 4, 6, 7]
  assert sort_list([3, 5, 1, 2])==[1, 2, 3, 5]
  assert sort_list([])==[]
  assert sort_list([9, 8, 7, 6, 5, 4, 3, 2, 1])==[1, 2, 3, 4, 5, 6, 7, 8, 9]
output: def sort_list(lst):
      for i in range(len(lst)):
          min_idx = i
          for j in range(i+1, len(lst)):
              if lst[j] < lst[min_idx]:
                  min_idx = j
          lst[i], lst[min_idx] = lst[min_idx], lst[i]
      return lst