final String key = "frontmatter." + entry.getKey();
            final List<String> values = entry.getValue();
            if (values != null && !values.isEmpty()) {
                extractData.putValues(key, values.toArray(new String[0]));
            }
        }
    }

    /**
     * Extracts heading text from the document.
     *
     * @param document the parsed Markdown document

     */
    public void putValues(final String key, final String[] values) {
        metadata.put(key, values);
    }

    /**
     * Puts a single value for a given key in the metadata.
     *
     * @param key the metadata key
     * @param value the value to associate with the key
     */
    public void putValue(final String key, final String value) {

                    StreamUtil.stream(getStringsByXPath(document, contentXpath)).get(stream -> stream.collect(Collectors.joining(" "))));
            metadataXpathMap.entrySet().stream().forEach(e -> {
                extractData.putValues(e.getKey(), getStringsByXPath(document, e.getValue()));
            });
            return extractData;
        } finally {
            xpathAPI.remove();
        }
    }

    /**

            if (extractMetadata) {
                for (final Map.Entry<String, List<String>> entry : metadataMap.entrySet()) {
                    final List<String> values = entry.getValue();
                    extractData.putValues(entry.getKey(), values.toArray(new String[0]));
                }
            }

            return extractData;
        } catch (final IOException e) {

  override fun invalidate() {
    delegate!!.invalidate()
  }

  override fun isValid(): Boolean = delegate!!.isValid

  override fun putValue(
    s: String,
    o: Any,
  ) {
    delegate!!.putValue(s, o)
  }

  override fun getValue(s: String): Any = delegate!!.getValue(s)

  override fun removeValue(s: String) {
    delegate!!.removeValue(s)
  }

  override fun getProtocol(): String = throw UnsupportedOperationException()

  override fun getSessionContext(): SSLSessionContext = throw UnsupportedOperationException()

  override fun putValue(
    s: String,
    obj: Any,
  ): Unit = throw UnsupportedOperationException()

  override fun removeValue(s: String): Unit = throw UnsupportedOperationException()