[checkpoints][xs]: save data so it's easy to develop new flows.

.gitignore

@@ -144,3 +144,6 @@ static
 
 # put you virtual env names here
 env36/
+
+# dataflows checkpoints
+.checkpoints/

process.py

@@ -23,6 +23,7 @@ Flow(
       load(f'{BASE_URL}{CONFIRMED}'),
       load(f'{BASE_URL}{RECOVERED}'),
       load(f'{BASE_URL}{DEATH}'),
+      checkpoint('load_data'),
       unpivot(unpivoting_fields, extra_keys, extra_value),
       find_replace([{'name': 'Date', 'patterns': [{'find': '/', 'replace': '-'}]}]),
       to_normal_date,