class_docstr: A wrapper for SphinxTestApp.
  
  This class is used to speed up the test by skipping ``app.build()``
  if it has already been built and there are any output files.
code: def build(self, *args: Any, **kwargs: Any) -> None:
      if not os.listdir(self.app.outdir):
          # if listdir is empty, do build.
          self.app.build(*args, **kwargs)
  
imports: from __future__ import annotations
  import contextlib
  import os
  import re
  import sys
  import warnings
  from typing import IO, TYPE_CHECKING, Any
  from xml.etree import ElementTree
  from docutils import nodes
  from sphinx import application
label_desc: Use image node_id 3 for calling the SphinxTestAppWrapperForSkipBuilding obj's underlying member method code with example usage: obj.build() without return types