A retrofit pickup assembly for stringed instruments is disclosed. The practice fish can detect a lure in two different modes, active or passive. The first diode element comprises a chalcogenide glass layer having a first conductivity type, the second diode element comprises a chalcogenide glass layer doped with an element such as bismuth and having a second conductivity type opposite to the first conductivity type and the memory cell comprises a chalcogenide glass element with silver ions therein. If the intersection of the file user set and the folder user set is an empty set, it is determined that determines that there is no user who can access the research object.