code: def get_latex(ink_filename):
      
      tex_file = os.path.splitext(ink_filename)[0] + ".tex"
      with open(tex_file) as f:
          tex_content = f.read().strip()
      pattern = re.compile(r"\\begin\{displaymath\}(.*?)\\end\{displaymath\}",
                           re.DOTALL)
      matches = pattern.findall(tex_content)
  
      if len(matches) == 0:
          pattern = re.compile(r"$$(.*?)$$",
                               re.DOTALL)
          matches = pattern.findall(tex_content)
  
      if len(matches) != 1:
          raise Exception("%s: Found not one match, but %i: %s" %
                          (ink_filename, len(matches), matches))
      formula_in_latex = matches[0].strip()
      formula_in_latex = remove_matching_braces(formula_in_latex)
  
      # repl = []
      # for letter in string.letters:
      #     repl.append(('\mbox{%s}' % letter, letter))
      # for search, replace in repl:
      #     formula_in_latex = formula_in_latex.replace(search, replace)
      return formula_in_latex
docs: Get the LaTeX string from a file by the *.ink filename.