input: Write a function called `reverse_string` that takes a string as an argument and returns the characters of the string in reverse order. The function should iterate through the string from the last character to the first, appending each character to a new string which will be returned as the result.
  
  def reverse_string(input_string):
      reversed_string = ''
      for i in range(len(input_string)-1, -1, -1):
          reversed_string += input_string[i]
      return reversed_string
  
  assert reverse_string("hello") == "olleh"
  assert reverse_string("Python") == "nohtyP"
  assert reverse_string("") == ""
  assert reverse_string("12345") == "54321"
  assert reverse_string("racecar") == "racecar"
output: def reverse_string(input_string):
      reversed_string = ''
      for i in range(len(input_string)-1, -1, -1):
          reversed_string += input_string[i]
      return reversed_string