The class, or its name (e.g. GraphicalMeasure.name). A name is unreliable in minified builds: they rename the classes, and give different classes the same name, e.g. "a" to GraphicalMeasure and GraphicalNote.
Puts the chord symbol back where it was before the first layout calculation, called before each calculation. MusicSheetCalculator.calculateChordSymbols() moves the chord symbol and its label, and moves a chord symbol that isn't over a note from its staff entry to its measure (parent), but the layout reads them before that, e.g. for the measure width needed for the chord symbols, for their x positions (MusicSheetCalculator.calculateChordSymbolsXPositions(), e.g. after the begin instructions of the measure), and for the bounding boxes, whose top and bottom borders only grow (BoundingBox.calculateTopBottomBorders()). Without the reset, a re-render would read the previous render's positions, parent and borders there, where the first render read the initial ones, and place the chord symbols (or e.g. the composer above them) differently. The first call takes the snapshot of the initial positions and parent.
Returns whether this object is an instance of the class, e.g. isInstanceOfClass(GraphicalMeasure).