docs: Document convertSelectorToDocument(Document selector) {
          Document document = new Document();
          for (String key : selector.keySet()) {
              if (key.startsWith("$")) {
                  continue;
              }
  
              Object value = selector.get(key);
              if (!Utils.containsQueryExpression(value)) {
                  Utils.changeSubdocumentValue(document, key, value, (AtomicReference<Integer>) null);
              }
          }
          return document;
      }