utes are usable
            when the generator expression is a <a class="link" href="../operator/sequence.html" title="Sequence Generator (a &lt;&lt; b)">Sequence
            (<code class="computeroutput"><span class="special">&lt;&lt;</span></code>)</a> only.
            In this case each of the attributes passed have to match the corresponding
            part of the sequence.
          </p>
<p>
            For the API functions deducing the correct (matching) generator type
            from the supplied 