display flat symbol in ees major

[Jinsong Zhao]

Hi there,

I am try to learn LilyPond by doing. I have a score, which display a 
flat symbol in ees major. However, I can't get that in LilyPond.

\version "2.19.15"
\relative c, {
  \clef "bass"
  \key ees \major
  c8 g' ees' g, c,4  < g'' bes, > |%m69
}

The last note in that score has a flat symbol. I think the last note may 
be ``beses,'', if so, the double flat symbol appears. How to get a flat 
symbol beside the note? Thank you very much for any suggestion or comments.

Best regards,
Jinsong