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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 append(self, decoration):
 """ Adds a text decoration on a CodeEdit instance :param decoration: Text decoration to add :type decoration: pyqode.core.api.TextDecoration """

        if decoration not in self._decorations:
            self._decorations.append(decoration)
            self._decorations = sorted(
                self._decorations, key=lambda sel: sel.draw_order)
            self.editor.setExtraSelections(self._decorations)
            return True
        return False