def _preprocess_args(self, task: LLMCompilerTask) -> None:
        """Replace dependency placeholders, i.e. ${1}, in task.args with the actual observation."""
        args = _replace_arg_mask_with_real_value(
            task.args, task.dependencies, self.tasks
        )
        task.args = args
Replace dependency placeholders, i.e. ${1}, in task.args with the actual observation.
llama-index-integrations/agent/llama-index-agent-llm-compiler/llama_index/agent/llm_compiler/task_fetching_unit.py