Transposition Confusion

[Thomas WillNot]

Hi,

I am having issues with transposition in my score for brass band.

LilyPond is likely working just how it should, but I have been reading about
it here
<http://lilypond.org/doc/v2.18/Documentation/notation/displaying-pitches#instrument-transpositions>,
and I just can't figure out what I should be doing differently!

Here is an small example from the trumpet part of my score:
\version "2.18.2"

\relative c''' {
  
  \transposition bes
   \key bes \major
    \time 2/2
         r4\f g-. d8-. c8-. g4-.
         c4-. d4-. r2
         r4 g-. d8-. c8-. g4-.
         c4-. d4-. r2
         r4 g-. d8-. c8-. g4-.
         c4-. d8-. g8-. d4-. c8-. g8-. }

I am using the score wizard from Frescobaldi, and this is pretty well the
way it set it up.  It is resulting in a part with two flats when there
should be none.  From what I am reading it seems like I am right to use
\transposition rather than \transpose since the notes are entered as they
look in the printed score.

Please let me know what I'm doing wrong!

Thanks,
    Thomas