public BooleanExpression isClosed() {
        if (closed == null) {
            closed = Expressions.booleanOperation(SpatialOps.IS_CLOSED, mixin);
        }
        return closed;
    }
Returns 1 (TRUE) if this MultiCurve is closed [StartPoint ( ) = EndPoint ( ) for each
Curve in this MultiCurve].

@return closed
querydsl-spatial/src/main/java/com/querydsl/spatial/jts/JTSMultiCurveExpression.java