update README with prompt invariance argument

README.md

@@ -26,6 +26,11 @@ The following will generate a CCS (Contrast Consistent Search) reporter instead
 elk elicit microsoft/deberta-v2-xxlarge-mnli imdb --net ccs
 ```
 
+To test prompt invariance across multiple datasets, use the `--combined_template_path` command line argument, which will create a new `templates.yaml` file with templates from all the datasets.
+```bash
+elk elicit bigscience/bloomz-560m christykoh/ag_news_pt ag_news --combined_template_path=spar_w/ag_news
+```
+
 The following command will evaluate the probe from the run naughty-northcutt on the hidden states extracted from the model deberta-v2-xxlarge-mnli for the imdb dataset. It will result in an `eval.csv` and `cfg.yaml` file, which are stored under a subfolder in `elk-reporters/naughty-northcutt/transfer_eval`.
 
 ```bash