kazuhiko-hotta

### Keybase proof

I hereby claim:

  * I am kazuhiko-hotta on github.
  * I am kazuhikohotta (https://keybase.io/kazuhikohotta) on keybase.
  * I have a public key ASBU6lefsivpCUkLjbsjm0KJzfm5QPB6m9SbSl5_5OZAlAo

To claim this, I am signing this object:

kazuhiko-hotta

from collections import defaultdict
from pprint import pprint

data = [{'order_id': [17], 'product_id': 763},
        {'order_id': [19], 'product_id': 822},
        {'order_id': [19], 'product_id': 822},
        {'order_id': [20], 'product_id': 994},
        {'order_id': [20], 'product_id': 783},
        {'order_id': [20], 'product_id': 783},
        {'order_id': [21], 'product_id': 857},