z3py: sequences

# for some reason this was missing from Z3py:
def Sequence(name, ctx=None):
    """Return a sequence constant named `name`. If `ctx=None`, then the global context is used.
    >>> x = Sequence('x')
    """
    ctx = z3.get_ctx(ctx)
    int_sort = z3.IntSort(ctx)
    return z3.SeqRef(
        z3.Z3_mk_const(ctx.ref(),
                       z3.to_symbol(name, ctx),
                       z3.SeqSortRef(z3.Z3_mk_seq_sort(int_sort.ctx_ref(), int_sort.ast)).ast),
        ctx)