input: Write a python function to convert a string to a list of numbers.
  assert convert_to_list("3, 17, 2, 9, 11") == [3, 17, 2, 9, 11]
  assert convert_to_list("1,2,3,4,5") == [1, 2, 3, 4, 5]
  assert convert_to_list("10, 20, 30, 40") == [10, 20, 30, 40]
output: def convert_to_list(s):
      return [int(x) for x in s.split(',')]