input: Write a function to split a string into a list of words with a specified maximum number of splits.
  assert split_string("Python is a great language", 3) == ['Python', 'is', 'a', 'great language']
  assert split_string("Write a python function to split", 2) == ['Write', 'a', 'python function to split']
  assert split_string("Test this function well", 1) == ['Test', 'this function well']
output: def split_string(s, max_splits):
      return s.split(' ', max_splits)