code: def replace_text_dir(self, directory, to_replace, replacement, file_type=None):
          
          if not file_type:
              file_type = "*.tex"
          for file in glob.iglob(os.path.join(directory, file_type)):
              self.replace_text(file, to_replace, replacement)
docs: Replaces a string with its replacement in all the files in the directory
  
          :param directory: the directory in which the files have to be modified
          :param to_replace: the string to be replaced in the files
          :param replacement: the string which replaces 'to_replace' in the files
          :param file_type: file pattern to match the files in which the string has to be replaced