How can i get a pdf from a PGraphic? It saves a file now but it's 0 bytes and can't be opened

3. import processing.pdf.*;
4. 
   
5. PGraphics pg;
6. 
   
7. void setup() {
8.   size(100, 100);
9.   pg = createGraphics(80, 80, PDF, "dump.pdf");
10.   
11.   pg.beginDraw();
12.   pg.background(102);
13.   pg.stroke(255);
14.   pg.line(0, 0, pg.width, pg.height);
15.   pg.endDraw();
16.   
17.    println("done");
18. 
    
19. }
20.