[Python] Write a recursive function recStrMerge() that takes two strings s1 and s2 as parameters and returns a string that consists of the two strings merged together. The string returned by the function should be the first character of s1 followed by the first character of s2, followed by the second character of s1 followed by the second character of s2, etc. If one string runs out of characters before the other, then the remaining string should appear at the end of the merged string. The only string functions you are allowed to use are len(), concatenation, indexing (s[i] for an integer i), or slicing (s[i:j] for integers i and j). The following shows several sample runs of the function:
recStrMerge('abc', 'xyz') -> 'axbycz'
recStrMerge('ahcd', '123456') -> 'a1h2c3d456'
recStrMerge('a$h', 'c*d(e)fghi') -> 'abc!123