d(<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</a>&nbsp;value)</pre>
<div class="block">Helper method that sub-classes may use to see if given String value is
 one of:
<ul>
 <li>YAML 1.1 keyword representing 
  <a href="https://yaml.org/type/bool.html">boolean</a>
  </li>
 <li>YAML 1.1 keyword representing 
  <a href="https://yaml.org/type/null.html">null</a> value
   </li>
 <li>empty String (length 0)
   </li>
</li