cement field is as follows:</p>
<pre>
<strong id="grammar-token-sf-replacement_field"><span id="grammar-token-replacement-field"></span>replacement_field</strong> ::=  &quot;{&quot; [<a class="reference internal" href="#grammar-token-sf-arg_id"><code class="xref docutils literal notranslate"><span class="pre">arg_id</span></code></a>] [&quot;:&quot; (<a class="reference internal" href="#grammar-token-sf-format_spec"><code class="xref docutils literal notranslate"><span class="pre">format_spec</span></code><