presto-parser/src/main/java/io/prestosql/sql/parser/AstBuilder.java/AstBuilder/visitBoundedFrame
class AstBuilder:    @Override
    public Node visitBoundedFrame(SqlBaseParser.BoundedFrameContext context)
    {
        return new FrameBound(getLocation(context), getBoundedFrameBoundType(context.boundType), (Expression) visit(context.expression()));
    }