docs: def _save_env(env):
      """Saves one environment.
  
      Args:
          env (dict): the env dict to save.
      """
      env_path = os.path.join(env["resultdir"], "env")
  
      if os.path.isdir(env["resultdir"]):
          with open(env_path, "w") as f:
              yaml.dump(env, f)