input: Write a python function to split a string into chunks of 5 characters.
  assert split_string("HelloWorldFromPython") == ["Hello", "World", "FromP", "ython"]
  assert split_string("ABCDE") == ["ABCDE"]
  assert split_string("PythonCode") == ["Pytho", "nCode"]
output: def split_string(s):
      return [s[i:i+5] for i in range(0, len(s), 5)]