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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 setPlainText(self, txt, mime_type, encoding):
 """ Extends setPlainText to force the user to setup an encoding and a mime type. Emits the new_text_set signal. :param txt: The new text to set. :param mime_type: Associated mimetype. Setting the mime will update the pygments lexer. :param encoding: text encoding """

        self.file.mimetype = mime_type
        self.file._encoding = encoding
        self._original_text = txt
        self._modified_lines.clear()
        import time
        t = time.time()
        super(CodeEdit, self).setPlainText(txt)
        _logger().log(5, 'setPlainText duration: %fs' % (time.time() - t))
        self.new_text_set.emit()
        self.redoAvailable.emit(False)
        self.undoAvailable.emit(False)