input: Write a function to sum the elements of a list up to a given position.
  assert sum_list_position([1, 3, 5, 4, 7], 3) == 13
  assert sum_list_position([10, 20, 30, 40, 50], 2) == 60
  assert sum_list_position([5, 10, 15, 20], 0) == 5
output: def sum_list_position(lst, pos):
      return sum(lst[:pos+1])