The function seems to map characters in the input string to specific characters in the output. The first character of the input string largely dictates the first character of the output, while numbers generally produce 'zDrD' as output. Further investigation is necessary to obtain the exact mapping rules.

To get a better understanding of the mapping rules, let's test more inputs, especially different string lengths and varied character types.

COMMAND: PYTHON(./temp/function.py "abcd" "ABCD" "1234" "@$%^&" "mix55" "l3tT3r")