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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 set_maintext(self, index):
 """Set the maintext_lb to display text information about the given reftrack :param index: the index :type index: :class:`QtGui.QModelIndex` :returns: None :rtype: None :raises: None """

        dr = QtCore.Qt.DisplayRole
        text = ""
        model = index.model()
        for i in (1, 2, 3, 5, 6):
            new = model.index(index.row(), i, index.parent()).data(dr)
            if new is not None:
                text = " | ".join((text, new)) if text else new

        self.maintext_lb.setText(text)