 class="extype" name="scala.Boolean">Boolean</span>)</span>
      </span>
      
      <p class="shortcomment cmt">Get the elements that are needed by the query target variables and the evidence variables.</p><div class="fullcomment"><div class="comment cmt"><p>Get the elements that are needed by the query target variables and the evidence variables. Also compute the values
of those variables to the given depth.
Only get factors for elements that are actually used by the target variables. This is more effic