How to convert .ICO to .PNG?

from cStringIO import StringIO
import Image
import urllib

def to_png(path, mime="png"):
    if path.startswith("http:"):
        url = urllib.quote(url)
        input = StringIO()
        input.write(urllib.urlopen(url).read())
        input.seek(0)
    else:
        input = open(path).read()

    if input:
        out  = StringIO()
        image = Image.open(input)
        image.save(out, mime.upper())
        return out.getvalue()
    else:
        return None