code: def _set_star_value(star_code, number_stars):
      
  
      for star in range(1, 6):
          if star <= number_stars:
              star_code = star_code.replace("fa fa-star " + str(star), "fa fa-star "
                                                                               "checked")
          else:
              star_code = star_code.replace("fa fa-star " + str(star), "fa fa-star")
  
      return star_code
docs: Internal function that is used for update the number of active stars (that define notebook
      difficulty level)
  
      ----------
      Parameters
      ----------
      star_code : str
          String with the HTML code to be changed.
  
      number_stars : int
          Number of stars that will be active.
  
      Returns
      -------
      out : str
          It is returned a string with the HTML code after updating the number of active stars.