input: Write a function to optimize a given Python script that reverses a string. If the input string is empty, the function should return an empty string. The function should use the most efficient method to reverse the string.
  assert reverse_string("hello") == "olleh"
  assert reverse_string("python") == "nohtyp"
  assert reverse_string("") == ""
output: def reverse_string(s):
      return s[::-1]