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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_jtimes_callback(self):
 """ Generate a callback fro evaluating the jacobian-vector product."""

        jtimes = self.get_jtimes()
        if jtimes is False:
            return None
        v, jtimes_exprs = jtimes
        return _Callback(self.indep, tuple(self.dep) + tuple(v), self.params,
                         jtimes_exprs, Lambdify=self.be.Lambdify)