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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 classifications_combo_box_changed( self, index, exposure, exposure_combo_box, edit_button):
 """Action when classification combo box changed. :param index: The index of the combo box. :type index: int :param exposure: The exposure associated with the combo box. :type exposure: dict :param exposure_combo_box: Combo box for the classification. :type exposure_combo_box: QComboBox :param edit_button: The edit button associate with combo box. :type edit_button: QPushButton """

        # Disable button if it's no classification
        edit_button.setEnabled(bool(index))

        classification = self.get_classification(exposure_combo_box)
        self.activate_classification(exposure, classification)
        clear_layout(self.right_layout)
        self.show_current_state()

        self.parent.pbnNext.setEnabled(self.is_ready_to_next_step())

        # Open edit panel directly
        edit_button.click()