input: Write a function to optimize a given Python script that reverses a string. The optimized function should use a more efficient method to achieve the same result.
  assert reverse_string("hello")=="olleh"
  assert reverse_string("world")=="dlrow"
  assert reverse_string("Python")=="nohtyP"
  assert reverse_string("")==""
  assert reverse_string("a")=="a"
output: def reverse_string(s):
      return s[::-1]