code: async def delete_pattern(self, pattern, count=None):
          
          cursor = '0'
          count_deleted = 0
          while cursor != 0:
              cursor, identities = await self.client.scan(
                  cursor=cursor, match=pattern, count=count
              )
              count_deleted += await self.client.delete(*identities)
          return count_deleted
docs: delete cache according to pattern in redis,
          delete `count` keys each time