remove accidental from a chord?

[Mark Polesky]

How do I properly remove one accidental from a chord? I found I
was able to replace the stencil with an empty-stencil, but there's
still a space left where it would have been.

I see that accidental-placement-interface has an internal property 
called accidental-grobs, but I don't know how to access it, or if
I could even change it from scheme if I wanted to.

Here's an example of what I was doing. Any help is appreciated.
- Mark

#(define (remove-middle-line-accidental grob)
   ;; Accidental stencil callback
   (if (eq? (ly:grob-property (ly:grob-property grob 'cause)
                              'staff-position) 0)
       empty-stencil
       (ly:accidental-interface::print grob)))

\relative {
  \once \override Accidental #'stencil =
    #remove-middle-line-accidental
  <ef gf bf df>
}

remove-accidental.png
Description: PNG image