Using -quiet through STL API

Hello,

I'm getting this error on quite a lot of files, while others work fine:

Magick: : unknown field with tag 33000 (0x80e8) encountered. 
`TIFFReadDirectory' @ warning/tiff.c/TIFFWarnings/706

I found this posting regarding it: 
http://www.imagemagick.org/discourse-server/viewtopic.php?f=3&t=18638

Although this relates to ImageMagick I was hoping that this might be 
relevant for GraphicsMagick, too. Our documents are scanned by a Fujitsu 
scanner and the document quality is improved by Kofax Virtual ReScan, so 
the "produced on a Kofax scanning station" situation of that post 
applies to us as well.

Now this post also states, that using convert (resp. "gm convert" in 
GraphicsMagick) with the option -quiet would disable this error and 
working with such documents would be mostly fine in the end.

How can I trigger this -quiet option when using the STL interface (I'm 
actually using python pgmagick, which in turn uses the STL interface)?

Kind regards
Marten

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