code: def get_template_language(self, file_):
          
          stem = Path(file_).stem
          language_code = stem.split('_')[-1:][0]
          if len(language_code) != 2:
              # TODO naive and temp implementation
              # check if the two chars correspond to one of the
              # available languages
              raise Exception('Template file `%s` must end in ISO_639-1 language code.' % file_)
          return language_code.lower()
docs: Return the template language
          Every template file must end in
          with the language code, and the
          code must match the ISO_6301 lang code
          https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
          valid examples:
  
          account_created_pt.html
          payment_created_en.txt