def _conversion_checks(self, item):
        """
        Internal use for checking if a duplicate safe attribute already exists

        :param item: Item to see if a dup exists
        """
        safe_item = self._safe_attr(item)

        if safe_item in self._box_config["__safe_keys"]:
            dups = [f"{item}({safe_item})", f'{self._box_config["__safe_keys"][safe_item]}({safe_item})']
            if self._box_config["box_duplicates"].startswith("warn"):
                warnings.warn(f"Duplicate conversion attributes exist: {dups}", BoxWarning)
            else:
                raise BoxError(f"Duplicate conversion attributes exist: {dups}")

        Internal use for checking if a duplicate safe attribute already exists

        :param item: Item to see if a dup exists
        
box/box.py