[BUG] Can't store concrete data classes that inherit from an abstract data class itself inheriting from ABC

[ericvergnaud]

Consider the following:

@dataclass
class AbstractDataclass(ABC):
  name: str

@dataclass
class ConcreteDataclass(AbstractDataclass):
 other: str

save_table will not store instances of ConcreteDataclass because ConcreteDataclass.__class__ is not a type
see backends.py line 350