input: Write a function to sort a list of strings and return the sorted list.
  assert sort_strings(['apple', 'mango', 'banana']) == ['apple', 'banana', 'mango']
  assert sort_strings(['delta', 'alpha', 'charlie', 'bravo']) == ['alpha', 'bravo', 'charlie', 'delta']
  assert sort_strings(['zebra', 'elephant', 'dog', 'cat']) == ['cat', 'dog', 'elephant', 'zebra']
output: def sort_strings(strings):
      return sorted(strings)