US 2019/0196326 Al  30  Jun.27,2019  [0215]  It is preferable that the lactone structure has a  repeating unit having a lactone structure represented by any  one of Formulae (LCl-1) to (LCl-17). The lactone structure  is preferably the lactone structure represented by Formula  (LCl-1), (LCl-4), (LCl-5), or (LCl-8) and more preferably  the lactone structure represented by Formula (LCl-4).  -continued  LCl-8  LCl-9  LCl-10  LCl-1  LCl-2  LCl-3  LCl-4  LCl-5  LCl-11  LCl-12  LCl-13  LCl-14  LCl-6  LCl-7  0  0  0  0 