Convert a path to the string representing the path
        Args:
            path (tuple): A tuple of arcs
        Returns:
            inp (str): The path concatenated as as string

def _path_to_str(self, path):
        """
        Convert a path to the string representing the path
        Args:
            path (tuple): A tuple of arcs
        Returns:
            inp (str): The path concatenated as as string
        """
        inp = ''
        for arc in path:
            i = self.isyms.find(arc.ilabel)
            # Ignore \epsilon transitions both on input
            if i != fst.EPSILON:
                inp += i
        return inp