Return all operations stored in containers.

def op_paths(self, path_base=None):
        # type: (Union[str, UrlPath]) -> Generator[Tuple[UrlPath, Operation]]
        """
        Return all operations stored in containers.
        """
        if path_base:
            path_base += self.path_prefix
        else:
            path_base = self.path_prefix or UrlPath()

        for container in self.containers:
            for op_path in container.op_paths(path_base):
                yield op_path