input: Write a python function to sort a list of strings in ascending order.
  assert sort_strings(['cat', 'apple', 'elephant', 'dog']) == ['apple', 'cat', 'dog', 'elephant']
  assert sort_strings(['banana', 'cherry', 'apple']) == ['apple', 'banana', 'cherry']
  assert sort_strings(['zebra', 'yak', 'aardvark']) == ['aardvark', 'yak', 'zebra']
output: def sort_strings(strings):
      return sorted(strings)