Write a function to mirror along the diagonal from (0, 0) to (width, height).

What will be an ideal response?

```
def mirrorDiagonal(source):
for y in range(0,getHeight(source)):
for x in range(y,getWidth(source)):
topPixel = getPixel(source ,x,y)
bottomPixel = getPixel(source,y,x)
color = getColor(topPixel)
setColor(bottomPixel ,color)
show(source)
```

Note: This function only works particularly well with square images.