code: public TerminalResult IS_NULL() {
  		getPredicateExpression().setOperator(Operator.IS_NULL);
  		TerminalResult ret = APIAccess.createTerminalResult(this.getPredicateExpression());
  		QueryRecorder.recordInvocation(this, "IS_NULL", ret);
  		return ret;
  	}
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>test against NULL (test if a property exists)</i></div>
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