human
Complete the below
def insensitize(string):

    ''''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.'
    '''

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What is a the Python program you requested?
assistant
#Here is the Python program you requested.
    def to_ins(match):
        char = match.group(1)
        return ('[%s%s]' % (char.lower(), char.upper()))
    return re.sub('([a-zA-Z])', to_ins, string)