Fix Index.query and Index.scan typing issues

[ikonst]

This now works again:

from pynamodb.attributes import NumberAttribute
from pynamodb.models import Model
from pynamodb.indexes import GlobalSecondaryIndex
from pynamodb.pagination import ResultIterator

class UntypedIndex(GlobalSecondaryIndex):
    bar = NumberAttribute(hash_key=True)

class MyModel(Model):
    foo = NumberAttribute(hash_key=True)
    bar = NumberAttribute()

    untyped_index = UntypedIndex()

# Ensure old code keeps working
untyped_result: ResultIterator = MyModel.untyped_index.query(123)
model: MyModel = next(untyped_result)
not_model: int = next(untyped_result)  # this is legacy behavior so it's "fine"

and then this is also possible now:

class TypedIndex(GlobalSecondaryIndex[MyModel]):
    #                                ^^^^^^^^^
    bar = NumberAttribute(hash_key=True)

class MyModel(Model):
    foo = NumberAttribute(hash_key=True)
    bar = NumberAttribute()

    typed_index = TypedIndex()

typed_result: ResultIterator[MyModel] = MyModel.typed_index.query(123)
my_model: MyModel = next(typed_result)
not_model: int = next(typed_result)  # E: Incompatible types in assignment (expression has type "MyModel", variable has type "int")

Ditto for scan.

[garrettheel]

Awesome. Nice work and thanks for the quick fix!