Fix typing in py3.7

Author: bonjourmauko

openfisca_core/periods/instant_.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Dict, Optional, Union
+from typing import Dict, Optional, Tuple, Union
 
 import calendar
 import datetime
@@ -9,7 +9,7 @@
 from ._units import DAY, MONTH, YEAR
 
 
-class Instant(tuple[int, int, int]):
+class Instant(Tuple[int, int, int]):
     """An instant in time (``year``, ``month``, ``day``).
 
     An ``Instant`` represents the most atomic and indivisible

openfisca_core/periods/period_.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Optional, Sequence, Union
+from typing import Optional, Sequence, Tuple, Union
 
 import calendar
 import datetime
@@ -10,7 +10,7 @@
 from .instant_ import Instant
 
 
-class Period(tuple[str, Instant, int]):
+class Period(Tuple[str, Instant, int]):
     """Toolbox to handle date intervals.
 
     A ``Period`` is a triple (``unit``, ``start``, ``size``).

openfisca_core/taxbenefitsystems/tax_benefit_system.py

@@ -399,10 +399,10 @@ def get_parameters_at_instant(
         key: Optional[types.Instant]
         msg: str
 
-        if isinstance(instant, Instant):
+        if isinstance(instant, types.Instant):
             key = instant
 
-        elif isinstance(instant, Period):
+        elif isinstance(instant, types.Period):
             key = instant.start
 
         elif isinstance(instant, (str, int)):