docs: static String generateFilenameForKey(SQLDatabase db, String keyString)
              throws NameGenerationException {
  
          String filename = null;
  
          long result = -1;  // -1 is error for insert call
          int tries = 0;
          while (result == -1 && tries < 200) {
              byte[] randomBytes = new byte[20];
              filenameRandom.nextBytes(randomBytes);
              String candidate = keyToString(randomBytes);
  
              ContentValues contentValues = new ContentValues();
              contentValues.put("key", keyString);
              contentValues.put("filename", candidate);
              result = db.insert(ATTACHMENTS_KEY_FILENAME, contentValues);
  
              if (result != -1) {  // i.e., insert worked, filename unique
                  filename = candidate;
              }
  
              tries++;
          }
  
          if (filename != null) {
              return filename;
          } else {
              throw new NameGenerationException(String.format(
                      "Couldn't generate unique filename for attachment with key %s", keyString));
          }
      }