input: Write a python function to split a string based on a given delimiter.
  assert split_string("apple,banana,grape", ",") == ["apple", "banana", "grape"]
  assert split_string("one|two|three", "|") == ["one", "two", "three"]
  assert split_string("hello world", " ") == ["hello", "world"]
output: def split_string(s, delimiter):
      return s.split(delimiter)