How can I override the getter for serial property?

CS.xml

<?xml version="1.0" encoding="UTF-8"?>
<Export generator="Cache" version="25" zv="Cache for Windows (x86-64) 2016.1 (Build 656U)" ts="2017-02-01 13:19:43">
<Class name="CS.Persistent">
<Super>%Persistent</Super>
<TimeChanged>64315,46718.639278</TimeChanged>
<TimeCreated>64315,46649.612714</TimeCreated>

<Property name="data">
<Type>CS.Serial</Type>
<SqlComputeCode>set {*} = ##class(CS.Persistent).dataGetStatic()</SqlComputeCode>
<SqlComputed>1</SqlComputed>
<Transient>1</Transient>
</Property>

<Method name="dataGet">
<Description>
data getter method in object context</Description>
<ReturnType>CS.Serial</ReturnType>
<Implementation><![CDATA[	return ..data2GetStatic()
]]></Implementation>
</Method>

<Method name="dataGetStatic">
<Description>
data getter method in SQL context</Description>
<ClassMethod>1</ClassMethod>
<ReturnType>CS.Serial</ReturnType>
<Implementation><![CDATA[	return $lb($lb("2017","01"),"CS.Serial")
]]></Implementation>
</Method>
</Class>


<Class name="CS.Serial">
<Super>%SerialObject</Super>
<TimeChanged>64315,46714.875846</TimeChanged>
<TimeCreated>64315,46567.947029</TimeCreated>

<Property name="Year">
<Type>%Integer</Type>
</Property>

<Property name="Month">
<Type>%Integer</Type>
</Property>
</Class>
</Export>