764         # Optional list argument

   764         # Optional list argument

   765         if v is not None:

   765         if v is not None:

   766             v = [field.strip().lower() for field in v.split(',')]

   766             v = [field.strip().lower() for field in v.split(',')]

   767     return k, v

   767     return k, v

   768 

   768 

   770     if v is None:

   771     if v is None:

   771         return str(k)

   772         return str(k)

   772     else:

   773     else:

   773         if k == 'no-cache' or k == 'private':

   774         if k == 'no-cache' or k == 'private':

   774             # quoted list of values

   775             # quoted list of values