input: Write a function to optimize a given Python script that reverses a string. The original function performs the reverse operation by iterating through each character of the string and appending it to a new string in reverse order. The optimized function should use a more efficient method.
  assert reverse_string("hello")=="olleh"
  assert reverse_string("Python")=="nohtyP"
  assert reverse_string("")==""
  assert reverse_string("12345")=="54321"
  assert reverse_string("a")=="a"
output: def reverse_string(s):
      return s[::-1]