def convertToLines(self, geometry):
        rings = self.getRings(geometry.constGet())
        output_wkb = self.convertWkbToLines(geometry.wkbType())
        out_geom = None
        if QgsWkbTypes.flatType(output_wkb) == QgsWkbTypes.MultiLineString:
            out_geom = QgsMultiLineString()
        else:
            out_geom = QgsMultiCurve()

        for ring in rings:
            out_geom.addGeometry(ring)

        return out_geom

 def convertToMultiLineStrings(self, geom):
     if QgsWkbTypes.geometryType(geom.wkbType()) == QgsWkbTypes.PointGeometry:
         raise QgsProcessingException(
             self.tr('Cannot convert from {0} to MultiLineStrings').format(QgsWkbTypes.displayString(geom.wkbType())))
     elif QgsWkbTypes.geometryType(geom.wkbType()) == QgsWkbTypes.LineGeometry:
         if QgsWkbTypes.isMultiType(geom.wkbType()):
             return [geom]
         else:
             # line to multiLine
             ml = QgsMultiLineString()
             ml.addGeometry(geom.constGet().clone())
             return [QgsGeometry(ml)]
     else:
         # polygons to multilinestring
         # we just use the boundary here - that consists of all rings in the (multi)polygon
         return [QgsGeometry(geom.constGet().boundary())]