Option declaration 021

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error"
                xmlns:p="http://www.w3.org/ns/xproc"
                xmlns:t="http://xproc.org/ns/testsuite/3.0"
                xmlns:xs="http://www.w3.org/2001/XMLSchema" version="3.0">
   <p:output port="result"/>
   <p:option name="option" required="false"
             select="'this is not a boolean'" as="xs:boolean"/>
   <p:identity>
      <p:with-input>
         <doc>{$option}</doc>
      </p:with-input>
   </p:identity>
</p:declare-step>