input: Write a function to reverse a given string. The function should iterate through the string from the end to the beginning and construct a new reversed string. The function name should be reverse_string and it should take one argument, input_string. It should return the reversed string.
  assert reverse_string("Python")=="nohtyP"
  assert reverse_string("Hello")=="olleH"
  assert reverse_string("12345")=="54321"
  assert reverse_string("reverse")=="esrever"
  assert reverse_string("")==""
output: def reverse_string(input_string):
      reversed_string = ""
      for char in input_string[::-1]:
          reversed_string += char
      return reversed_string