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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 _init_titles(self):
 """ Init Titles if not defined """

        super(ModelRestApi, self)._init_titles()
        class_name = self.datamodel.model_name
        if not self.list_title:
            self.list_title = "List " + self._prettify_name(class_name)
        if not self.add_title:
            self.add_title = "Add " + self._prettify_name(class_name)
        if not self.edit_title:
            self.edit_title = "Edit " + self._prettify_name(class_name)
        if not self.show_title:
            self.show_title = "Show " + self._prettify_name(class_name)
        self.title = self.list_title