code: public Concat WHERE() {
  		Concat concat = PFactory.createConcat();
  		PredicateExpression px = (PredicateExpression) APIObjectAccess.getAstNode(concat);
  		CollectExpression collXpr = (CollectExpression)this.astNode;
  		((PredicateEvalExpression)collXpr.getEvalExpression())
  				.setPredicateExpression(px);
  		px.setContainingCollectExpression(collXpr);
  		return concat;
  	}
docs: <div color='red' style="font-size:24px;color:red"><b><i><u>JCYPHER</u></i></b></div>
  <div color='red' style="font-size:18px;color:red"><i>start a predicate expression which is evaluated against each element of a collection</i></div>
  <div color='red' style="font-size:18px;color:red"><i>e.g. ...holdsTrue(I.forAll(n)...<b>WHERE()</b>...</i></div>
  <br/>