code> column in the input has been
converted to (one or more) columns containing draws from those <code><a href="https://mc-stan.org/posterior/reference/rvar.html" class="external-link">rvar</a></code>s
in long format. The result is grouped by all non-<code><a href="https://mc-stan.org/posterior/reference/rvar.html" class="external-link">rvar</a></code> columns in the
input; this ensures that <code>nest_rvars(unnest_rvars(x))</code> returns <code>x</code>.</p>
    </div>

    <div id="ref-examples">
    <h2