docs: 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)