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Complete this python program:
def kernS(s):
assistant
#Here is the Python program you requested.

    """Use a hack to try keep autosimplification from joining Integer or
    minus sign into an Add of a Mul; this modification doesn\t
    prevent the 2-arg Mul from becoming an Add, however.
    Examples
    >>> from sympy.core.sympify import kernS
    >>> from sympy.abc import x, y, z
    The 2-arg Mul allows a leading Integer to be distributed but kernS will
    prevent that:
    >>> 2*(x + y)
    2*x + 2*y
    >>> kernS(\2*(x + y)\)
    2*(x + y)
    If use of the hack fails, the un-hacked string will be passed to sympify...
    and you get what you get.
    XXX This hack should not be necessary once issue 4596 has been resolved.
    """
    import re
    from sympy.core.symbol import Symbol
    hit = False
    if ('(' in s):
        if (s.count('(') != s.count(')')):
            raise SympifyError('unmatched    left    parenthesis')
        kern = '_kern'
        while (kern in s):
            kern += '_'
        olds = s
        s = re.sub('(\\d+)(    *\\*    *)\\(', ('\\1*%s\\2(' % kern), s)
        kern2 = (kern + '2')
        while (kern2 in s):
            kern2 += '_'
        target = ('%s-%s*(' % (kern, kern))
        s = re.sub('-    *\\(', target, s)
        i = nest = 0
        while True:
            j = s.find(target, i)
            if (j == (-1)):
                break
            j = s.find('(')
            for j in range(j, len(s)):
                if (s[j] == '('):
                    nest += 1
                elif (s[j] == ')'):
                    nest -= 1
                if (nest == 0):
                    break
            s = ((s[:j] + kern2) + s[j:])
            i = j
        s = s.replace(target, target.replace(kern, '(', 1))
        s = s.replace(kern2, ')')
        hit = (kern in s)
    for i in range(2):
        try:
            expr = sympify(s)
            break
        except:
            if hit:
                s = olds
                hit = False
                continue
            expr = sympify(s)
    if (not hit):
        return expr
    rep = {Symbol(kern): 1}
    def _clear(expr):
        if isinstance(expr, (list, tuple, set)):
            return type(expr)([_clear(e) for e in expr])
        if hasattr(expr, 'subs'):
            return expr.subs(rep, hack2=True)
        return expr
    expr = _clear(expr)
    return expr