Method __init__

lib/sqlalchemy/sql/selectable.py:7197–7222

(
        self,
        __argument: Optional[
            Union[_ColumnsClauseArgument[Any], SelectBase, ScalarSelect[Any]]
        ] = None,
        /,
    )

    inherit_cache = True

    def __init__(
        self,
        __argument: Optional[
            Union[_ColumnsClauseArgument[Any], SelectBase, ScalarSelect[Any]]
        ] = None,
        /,
    ):
        s: ScalarSelect[Any]

        # TODO: this seems like we should be using coercions for this
        if __argument is None:
            s = Select(literal_column("*")).scalar_subquery()
        elif isinstance(__argument, SelectBase):
            s = __argument.scalar_subquery()
            s._propagate_attrs = __argument._propagate_attrs
        elif isinstance(__argument, ScalarSelect):
            s = __argument
        else:
            s = Select(__argument).scalar_subquery()

        UnaryExpression.__init__(
            self,
            s,
            operator=operators.exists,
            type_=type_api.BOOLEANTYPE,
        )

    @util.ro_non_memoized_property
    def _from_objects(self) -> List[FromClause]: