human
Complete this python program:
def insensitize(string):
assistant
#Here is the Python code you requested.

    """Change upper and lowercase letters to be case insensitive in
    the provided string.  e.g., \a\ becomes \[Aa]\, \B\ becomes
    \[bB]\, etc.  Use for building regexes.
    """
    def to_ins(match):
        char = match.group(1)
        return ('[%s%s]' % (char.lower(), char.upper()))
    return re.sub('([a-zA-Z])', to_ins, string)