docs: def save(self, value, redis, *, commit=True):
          ''' Sets this fields value in the databse '''
          value = self.prepare(value)
  
          if value is not None:
              redis.hset(self.obj.key(), self.name, value)
          else:
              redis.hdel(self.obj.key(), self.name)
  
          if self.index:
              key = self.key()
  
              if self.name in self.obj._old:
                  redis.hdel(key, self.obj._old[self.name])
  
              if value is not None:
                  redis.hset(key, value, self.obj.id)