input: Write a function to optimize a given Python script that reverses a string. The optimized function should return the reversed string using a more efficient method.
  def reverse_string(string):
      return string[::-1]
  assert reverse_string("hello")=="olleh"
  assert reverse_string("python")=="nohtyp"
  assert reverse_string("")==""
  assert reverse_string("a")=="a"
  assert reverse_string("12345")=="54321"
output: def reverse_string(string):
      return string[::-1]