Bool required
If this flag is TRUE, then files saved to disk will be written assuming that, when the file is read from disk, the class will always be present.
This is useful for shrinking the size of saved files if there are very many snips from the class in a buffer; however, if the class turns out to not be present at load time, the file will not be readable at all. The value of required should never change. You should generally set this field to FALSE.