from pynamodb.attributes import UnicodeAttribute
from pynamodb.models import Model
class MyModel(Model):
  my_key = UnicodeAttribute()
  my_value = UnicodeAttribute(null=True)
...
my_model = MyModel.get('key')
if my_model.my_value.lower() == 'foo':  # error: Item "None" of "Optional[str]" has no attribute "lower"
   print("Value is foo")

if my_model.my_value and my_model.my_value.lower() == 'foo':
   print("Value is foo")

from pynamodb.models import Model
from pynamodb.attributes import NumberAttribute
from pynamodb.attributes import UnicodeAttribute
class MyModel(Model):
  my_key = UnicodeAttribute(hash_key=True)
  my_value = NumberAttribute(null=True)
# Existing attributes would be enforced:
_ = MyModel(my_key='key', my_value=42, my_other_value='other_value')  # error: Unexpected keyword argument "my_other_value" for "MyModel"
# Typing would be enforced:
_ = MyModel(my_key='key', my_value='42')  # error: Argument 2 to "MyModel" has incompatible type "str"; expected "Optional[int]"
# Nullability will be enforced::
_ = MyModel(my_key='key', my_value=None)
_ = MyModel(my_key=None, my_value=None)  # error: Argument "my_key" to "MyModel" has incompatible type "None"; expected "str"
# The hash key and range key can also be passed as positional arguments:
_ = MyModel('key')
_ = MyModel(42)  # error: Argument 1 to "MyModel" has incompatible type "int"; expected "str"