  <th>first_stage</th>
      <td><p>formula for Y(0)</p></td>
    </tr>
    <tr>
      <th>weights</th>
      <td><p>estimation weights for observations. This is used in estimating Y(0) and also augments treatment effect weights</p></td>
    </tr>
    <tr>
      <th>wtr</th>
      <td><p>character vector of treatment weight names (see horizon/allhorizon for standard event study weights)</p></td>
    </tr>
    <tr>
      <th>horizon</th>
      <td><p>vector of event_time. This only applies if wtr is left as 