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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 check_selection_for_save(self, task, releasetype, descriptor):
 """Emit warnings if the descriptor is None or the current file is of a different task. :param task: the selected task :type task: :class:`djadapter.models.Task` :param releasetype: the releasetype to save (probably work) :type releasetype: str :param descriptor: the descriptor :type descriptor: str :returns: True if check was successfull. :rtype: bool :raises: None """

        if not descriptor:
            self.statusbar.showMessage("Please provide a descriptor!")
            return False
        try:
            jukedj.validators.alphanum_vld(descriptor)
        except ValidationError:
            self.statusbar.showMessage("Descriptor contains characters other than alphanumerical ones.")
            return False
        cur = self.get_current_file()
        if cur and task != cur.task:
            self.statusbar.showMessage("Task is different. Not supported atm!")
            return False
        elif cur and releasetype != cur.releasetype:
            self.statusbar.showMessage("Releasetype is different. Not supported atm!")
            return False
        return True