input: Write a function to optimize a given Python script that reverses a string. The original function iterates through each character of the string and constructs the reversed string by appending each character to the beginning of the result. The optimized function should use a more efficient method to reverse the string.
  
  assert reverse_string("hello")=="olleh"
  assert reverse_string("world")=="dlrow"
  assert reverse_string("")==""
  assert reverse_string("12345")=="54321"
  assert reverse_string("a")=="a"
output: def reverse_string(s):
      return s[::-1]