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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 _pre_activate_injection(self):
 """ Injects functions before the activation routine of child classes gets called """

        # Let's be sure that this plugins class is registered and available on application level under
        # application.plugins.classes. This allows to reuse this class for *new* plugins.
        if not self.app.plugins.classes.exist(self.__class__.__name__):
            self.app.plugins.classes.register([self.__class__])

        self._load_needed_plugins()

        self.app.signals.send("plugin_activate_pre", self)