code: public T byExpression() {
  		ModifyExpression mx = (ModifyExpression)this.astNode;
  		mx.setValue(null);
  		return this.connector;
  	}
docs: <div color='red' style="font-size:24px;color:red"><b><i>JCYPHER LANGUAGE ELEMENT</i></b></div>
  <div color='red' style="font-size:18px;color:red"><i>set by an Expression which is constructed out of clauses which directly follow the <b>byExpression()</b></i></div>
  <div color='red' style="font-size:18px;color:red"><i>e.g. <b>CASE .. WHEN ..</b></i></div>
  <br/>