docs: def _load_latex2unicode_constants(kb_file=None):
      """Load LaTeX2Unicode translation table dictionary.
  
      Load LaTeX2Unicode translation table dictionary and regular
      expression object from KB to a global dictionary.
  
      :param kb_file: full path to file containing latex2unicode translations.
                      Defaults to CFG_ETCDIR/bibconvert/KB/latex-to-unicode.kb
      :type kb_file: string
  
      :return: dict of type: {'regexp_obj': regexp match object,
                              'table': dict of LaTeX -> Unicode mappings}
      :rtype: dict
      """
      if kb_file is None:
          kb_file = get_kb_filename()
  
      try:
          data = open(kb_file)
      except IOError:
          # File not found or similar
          sys.stderr.write(
              "\nCould not open LaTeX to Unicode KB file. "
              "Aborting translation.\n")
          return CFG_LATEX_UNICODE_TRANSLATION_CONST
      latex_symbols = []
      translation_table = {}
      for line in data:
          # The file has form of latex|--|utf-8. First decode to Unicode.
          line = line.decode('utf-8')
          mapping = line.split('|--|')
          translation_table[mapping[0].rstrip('\n')] = mapping[1].rstrip('\n')
          latex_symbols.append(re.escape(mapping[0].rstrip('\n')))
      data.close()
      CFG_LATEX_UNICODE_TRANSLATION_CONST[
          'regexp_obj'] = re.compile("|".join(latex_symbols))
      CFG_LATEX_UNICODE_TRANSLATION_CONST['table'] = translation_table