"""
datalite.constraints module introduces constraint
types that can be used to hint field variables,
that can be used to signal datalite decorator
constraints in the database.
"""
from typing import Tuple, TypeVar, Union
T = TypeVar("T")
[Doku]
class ConstraintFailedError(Exception):
"""
This exception is raised when a Constraint fails.
"""
Unique = Union[Tuple[T], T] # type: ignore
"""
Dataclass fields hinted with this type signals
datalite that the bound column of this
field in the table is NOT NULL and UNIQUE.
"""