<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def evaluate_objective(self):
 """ Evaluates the objective """

        self.Y_new, cost_new = self.objective.evaluate(self.suggested_sample)
        self.cost.update_cost_model(self.suggested_sample, cost_new)
        self.Y = np.vstack((self.Y,self.Y_new))