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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 batch_eval(self, exprs, n, extra_constraints=(), solver=None, model_callback=None):
 """ Evaluate one or multiple expressions. :param exprs: A list of expressions to evaluate. :param n: Number of different solutions to return. :param extra_constraints: Extra constraints (as ASTs) to add to the solver for this solve. :param solver: A solver object, native to the backend, to assist in the evaluation. :param model_callback: a function that will be executed with recovered models (if any) :return: A list of up to n tuples, where each tuple is a solution for all expressions. """

        if self._solver_required and solver is None:
            raise BackendError("%s requires a solver for batch evaluation" % self.__class__.__name__)

        converted_exprs = [ self.convert(ex) for ex in exprs ]

        return self._batch_eval(
            converted_exprs, n, extra_constraints=self.convert_list(extra_constraints),
            solver=solver, model_callback=model_callback
        )