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Fig 1. Example of UIContraints (an example from system-config-printer)
Very thick paper can't pass duplexer physically reason
So Duplex function is disabled
Really thick
Paper selected
Ricoh-Aficio_SP_C831DN-Postscript-Ricoh.ppd
*UIConstraints: *Duplex DuplexTumble *MediaType Thick4
*UIConstraints: *MediaType Thick4 *Duplex DuplexTumble