@Override
  public @NotNull Element getState() {
    Element state = new Element(STATE_TAG);
    for (String id : myRecentExpressions.keySet()) {
      LinkedList<XExpression> expressions = myRecentExpressions.get(id);
      List<ExpressionState> states = ContainerUtil.map(expressions, ExpressionState::new);
      Element entryElement = new Element(EXPRESSIONS_TAG);
      entryElement.setAttribute(ID_ATTRIBUTE, id);
      for (ExpressionState expressionState : states) {
        entryElement.addContent(XmlSerializer.serialize(expressionState));
      }
      state.addContent(entryElement);
    }
    return state;
  }
@Override
  public @NotNull Element getState()