@Override
  protected void serialize(Person p) {

    ArrayList<String> arguments = new ArrayList<String>();

    arguments.add(Long.toString(p.accountId()));
    arguments.add(p.firstName() + " " + p.lastName());
    writers[FileNames.PERSON.ordinal()].writeEntry(arguments);
  }
  @Override
  protected void serialize(Person p, Knows knows) {
    ArrayList<String> arguments = new ArrayList<String>();

    arguments.add(Long.toString(p.accountId()));
    arguments.add(Long.toString(knows.to().accountId()));
    writers[FileNames.PERSON_KNOWS_PERSON.ordinal()].writeEntry(arguments);
  }