The function appears to replace each alphabet character with a mirror image. It swaps 'a' with 'z', 'b' with 'y', and so on. Other characters, like numbers, spaces, and symbols, seem to be unchanged.

[CODE]: 

```python
def mirror_function(s):
    result = []
    for c in s:
        if c.isalpha():
            idx = ord(c.lower()) - ord('a')
            new_char = chr(ord('z') - idx)
            if c.isupper():
                new_char = new_char.upper()
            result.append(new_char)
        else:
            result.append(c)
    return ''.join(result)
```