class_docstr: Override `HTMLExtractor` and create `etree` `Elements` for any elements which should have content parsed as
  Markdown.
docstr: Return element from `treebuilder` and reset `treebuilder` for later use. 
code: def get_element(self) -> etree.Element:
      """Return element from `treebuilder` and reset `treebuilder` for later use."""
      element = self.treebuilder.close()
      self.treebuilder = etree.TreeBuilder()
      return element
  
imports: from __future__ import annotations
  from .None import Extension
  from ..blockprocessors import BlockProcessor
  from ..preprocessors import Preprocessor
  from ..postprocessors import RawHtmlPostprocessor
  from ..None import util
  from ..htmlparser import HTMLExtractor, blank_line_re
  import xml.etree.ElementTree
  from typing import TYPE_CHECKING, Literal, Mapping
label_desc: Use image node_id 4 for calling the HTMLExtractorExtra obj's underlying member method code with example usage: obj.get_element() and returns: element