code: public RElement<RElement<?>> stdevp(JcProperty property) {
  		ReturnExpression rx = getReturnExpression();
  		ReturnAggregate ra = (ReturnAggregate) rx.getReturnValue();
  		ra.setType(AggregateFunctionType.STDEVP);
  		ra.setArgument(property);
  		RElement<RElement<?>> ret = new RElement<RElement<?>>(rx);
  		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> calculate the standard deviation for a given value over a group;
  <br/>uses a standard two-pass method, with N - 1 as the denominator,
  and should be used when taking a sample of an entire population.</i></div>
  <div color='red' style="font-size:18px;color:red"><i>e.g. ...aggregate().<b>stdevp(n.property("age"))</b></i></div>
  <br/>