code: def hkl_tuple_to_str(hkl):
      
      str_format = '($'
      for x in hkl:
          if x < 0:
              str_format += '\\overline{' + str(-x) + '}'
          else:
              str_format += str(x)
      str_format += '$)'
      return str_format
docs: Prepare for display on plots
      "(hkl)" for surfaces
      Agrs:
          hkl: in the form of [h, k, l] or (h, k, l)