def __init__(self, _db=None, _instance=None):
        """A class that performs queries using SQLAlchemy based on specified models.

        Args:
            _db: The SQLAlchemy database session.
        """
        self._db = _db
        self._instance = _instance

    def get_mode_fields(self, fields: str, test_mode_switch: str = "off") -> str | None:
        """Return fields using the specified model.

        Args:
            model: The SQLAlchemy model class to use for the query.
            test_mode_switch (str, optional): Value on/off, Defaults to "off" .

        Returns:
            Query: string attr.
        """
        try:
            test_mode = util.strtobool(test_mode_switch)
            return self.SECONDARY_FIELDS.get(fields) if test_mode else self.MAIN_FIELDS.get(fields)

        except (ValueError, AttributeError):
            return self.MAIN_FIELDS.get(fields)

    def get_inner_instance(self, test_mode_switch: str = "off"):
        """
        Return instance using the specified model.

        Args:
            model: The SQLAlchemy model class to use for the query.

        Returns:
            Query: The SQLAlchemy query object.
        """
        if self._instance:
            try:
                test_mode = util.strtobool(test_mode_switch)
                return (
                    self.SECONDARY_MODELS.get(self._instance.__tablename__)
                    if test_mode
                    else self.MAIN_MODELS.get(self._instance.__tablename__)
                )

            except (ValueError, AttributeError):
                return self.MAIN_MODELS.get(self._instance.__tablename__)

        return None

    @classmethod
    def get_instance(cls, _instance, test_mode_switch: str = "off"):
        """
        Return instance using the specified model.

        Args:
            model: The SQLAlchemy model class to use for the query.

        Returns:
            Query: The SQLAlchemy query object.
        """
        if _instance:
            try:
                test_mode = util.strtobool(test_mode_switch)
                return (
                    cls.SECONDARY_MODELS.get(_instance.__tablename__)
                    if test_mode
                    else cls.MAIN_MODELS.get(_instance.__tablename__)
                )

            except (ValueError, AttributeError):
                return cls.MAIN_MODELS.get(_instance.__tablename__)

        return None

    def query(self, test_mode_switch: str = "off"):
        """
        Executes a query using the specified model.

        Args:
            model: The SQLAlchemy model class to use for the query.

        Returns:
            Query: The SQLAlchemy query object.
        """
        if not self._instance:
            try:
                test_mode = util.strtobool(test_mode_switch)
                return (
                    self._db.query(self.SECONDARY_MODELS.get(self._instance.__tablename__))
                    if test_mode
                    else self._db.query(self.MAIN_MODELS.get(self._instance.__tablename__))
                )

            except (ValueError, AttributeError):
                return self._db.query(self.MAIN_MODELS.get(self._instance.__tablename__))

        return None

    @staticmethod
    def is_test_mode(test_mode_switch: str = "off") -> bool | int:
        """Check test_mode_switch

        Args:
            test_mode_switch (str, optional): Defaults to "off".

        Returns:
            bool: True/False
        """
        try:
            test_mode = util.strtobool(test_mode_switch)
            return test_mode

        except (ValueError, AttributeError):
            return False