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Complete this python program:
def continued_fraction_reduce(cf):
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#Here is the Python code you requested.

    """Reduce a continued fraction to a rational or quadratic irrational.
    Compute the rational or quadratic irrational number from its
    terminating or periodic continued fraction expansion.  The
    continued fraction expansion (cf) should be supplied as a
    terminating iterator supplying the terms of the expansion.  For
    terminating continued fractions, this is equivalent to
    ``list(continued_fraction_convergents(cf))[-1]``, only a little more
    efficient.  If the expansion has a repeating part, a list of the
    repeating terms should be returned as the last element from the
    iterator.  This is the format returned by
    continued_fraction_periodic.
    For quadratic irrationals, returns the largest solution found,
    which is generally the one sought, if the fraction is in canonical
    form (all terms positive except possibly the first).
    Examples
    >>> from sympy.ntheory.continued_fraction import continued_fraction_reduce
    >>> continued_fraction_reduce([1, 2, 3, 4, 5])
    225/157
    >>> continued_fraction_reduce([-2, 1, 9, 7, 1, 2])
    -256/233
    >>> continued_fraction_reduce([2, 1, 2, 1, 1, 4, 1, 1, 6, 1, 1, 8]).n(10)
    2.718281835
    >>> continued_fraction_reduce([1, 4, 2, [3, 1]])
    (sqrt(21) + 287)/238
    >>> continued_fraction_reduce([[1]])
    1/2 + sqrt(5)/2
    >>> from sympy.ntheory.continued_fraction import continued_fraction_periodic
    >>> continued_fraction_reduce(continued_fraction_periodic(8, 5, 13))
    (sqrt(13) + 8)/5
    See Also
    continued_fraction_periodic
    """
    from sympy.core.symbol import Dummy
    from sympy.solvers import solve
    period = []
    x = Dummy('x')
    def untillist(cf):
        for nxt in cf:
            if isinstance(nxt, list):
                period.extend(nxt)
                (yield x)
                break
            (yield nxt)
    a = Integer(0)
    for a in continued_fraction_convergents(untillist(cf)):
        pass
    if period:
        y = Dummy('y')
        solns = solve((continued_fraction_reduce((period + [y])) - y), y)
        solns.sort()
        pure = solns[(-1)]
        return a.subs(x, pure).radsimp()
    else:
        return a