Assign **layerName** to the layer currently named
        **otherLayerName** and assign the name **otherLayerName**
        to the layer currently named **layerName**.

            >>> font.swapLayerNames("before drawing revisions", "after drawing revisions")

def swapLayerNames(self, layerName, otherLayerName):
        """
        Assign **layerName** to the layer currently named
        **otherLayerName** and assign the name **otherLayerName**
        to the layer currently named **layerName**.

            >>> font.swapLayerNames("before drawing revisions", "after drawing revisions")
        """
        layerOrder = self.layerOrder
        layerName = normalizers.normalizeLayerName(layerName)
        if layerName not in layerOrder:
            raise ValueError("No layer with the name '%s' exists." % layerName)
        otherLayerName = normalizers.normalizeLayerName(otherLayerName)
        if otherLayerName not in layerOrder:
            raise ValueError("No layer with the name '%s' exists." % otherLayerName)
        self._swapLayers(layerName, otherLayerName)