ated after <code class="code">unsafe_to_string</code> is called. The
   <code class="code">string_init</code> code gives up ownership of <code class="code">s</code>, and returns the
   ownership of the resulting string to its caller.</p>

<p>Note that it would be unsafe if <code class="code">s</code> was passed as an additional
   parameter to the function <code class="code">f</code> as it could escape this way and be
   mutated in the future -- <code class="code">string_init</code> would give up ownership 