Unmix My Strings

Unmix My Strings

lPaeesh le pemu mnxit ehess rtnisg! Oh, sorry, that was supposed to say: Please help me unmix these strings! Somehow my strings have all become mixed up; every pair of characters has been swapped. Help me undo this so I can understand my strings again. 

 unmix("123456") ➞ "214365" 
 unmix("hTsii  s aimex dpus rtni.g") ➞ "This is a mixed up string." 
 unmix("badce") ➞ "abcde" 

Input: hTsii s aimex dpus rtni.g, Output: This is a mixed up string. 

Input: 214365, Output: 123456 

Input: badce, Output: abcde 

Question Reference: https://edabit.com/challenge/XRAGxXj4KtakkvD3F