def retrieve_from_cache(self):
        """Try to retrieve the node's content from a cache

        This method is called from multiple threads in a parallel build,
        so only do thread safe stuff here. Do thread unsafe stuff in
        built().

        Returns true if the node was successfully retrieved.
        """
        if self.nocache:
            return None
        if not self.is_derived():
            return None
        return self.get_build_env().get_CacheDir().retrieve(self)
Try to retrieve the node's content from a cache

        This method is called from multiple threads in a parallel build,
        so only do thread safe stuff here. Do thread unsafe stuff in
        built().

        Returns true if the node was successfully retrieved.