input: Write a function to convert a given string to a list of integers. The string will be a comma-separated list of numbers. If the input string is empty, the function should return an empty list.
  def to_int_list(s):
      return [int(x) for x in s.split(',')]
  assert to_int_list("1,2,3,4")==[1, 2, 3, 4]
  assert to_int_list("0,10,20,30")==[0, 10, 20, 30]
  assert to_int_list("")==[]
  assert to_int_list("5")==[5]
  assert to_int_list("100,200,300")==[100, 200, 300]
output: def to_int_list(s):
      return [int(x) for x in s.split(',') if x]