def to_triple(self, fmt: str = "medium") -> dict:
        """Convert AST object to BEL triple

        Args:
            fmt (str): short, medium, long formatted BEL statements
                short = short function and short relation format
                medium = short function and long relation format
                long = long function and long relation format

        Returns:
            dict: {'subject': <subject>, 'relation': <relations>, 'object': <object>}
        """

        if self.ast:
            return self.ast.to_triple(ast_obj=self.ast, fmt=fmt)
        else:
            return {}