clarify docs for pv.Viewer.quality
clarify docs for pv.Viewer.quality

Traksewt/pv,Traksewt/pv,CyrusBiotechnology/pv,CyrusBiotechnology/pv,biasmv/pv,Traksewt/pv,yuhangwang/pv,CyrusBiotechnology/pv,CyrusBiotechnology/pv,Traksewt/pv,yuhangwang/pv,biasmv/pv,yuhangwang/pv,yuhangwang/pv,biasmv/pv,biasmv/pv