code: def find_root_tex_document(base_dir="."):
      
      log = logging.getLogger(__name__)
      for tex_path in iter_tex_documents(base_dir=base_dir):
          with codecs.open(tex_path, 'r', encoding='utf-8') as f:
              text = f.read()
              if len(docclass_pattern.findall(text)) > 0:
                  log.debug("Found root tex {0}".format(tex_path))
                  return tex_path
      log.warning("Could not find a root .tex file")
      raise RootNotFound
docs: Find the tex article in the current directory that can be considered
      a root. We do this by searching contents for ``'\documentclass'``.
  
      Parameters
      ----------
      base_dir : str
          Directory to search for LaTeX documents, relative to the current
          working directory.
  
      Returns
      -------
      tex_path : str
          Path to the root tex document relative to the current
          working directory.