input: Write a function to reverse a string in place.
  assert reverse_string_in_space("Hello World!") == "!dlroW olleH"
  assert reverse_string_in_space("abcdef") == "fedcba"
  assert reverse_string_in_space("12345") == "54321"
output: def reverse_string_in_space(s):
      return s[::-1]