Error XD0062-003

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" name="main" version="3.0">
   <p:output port="result"/>
   <p:identity>
      <p:with-input>
         <p:inline document-properties="map{'content-type' : 'text/plain'}">This is no text document.</p:inline>
      </p:with-input>
   </p:identity>
</p:declare-step>