What i want:

I want to inherit the model(account.invoice) qweb report named as report_invoice_document which i access by Purchase->Vendor Bills then Print invoice of Vendor Bills.

What i had done till now

I am trying to inherit a qweb Report which relates to model (account.invoice). I simply goes to settings->reports and found my qweb template which need to be inherited. Here is the screenshoot.

https://i.stack.imgur.com/2wsoC.png

Further i dig into my reports. I had successfully found my report named as account.report_invoice_document. here is the screenshot 

https://i.stack.imgur.com/UHDUx.png

I had successfully inherited my required view and it shows me that i had tried to inherit then view in inherited views. here is the screenshot 

https://i.stack.imgur.com/FBphm.png

here is my code in which i had inherited the existing view.

<template id="myinherited_account_invoice_report" inherit_id="account.report_invoice_document">
            <xpath expr="//table[@class='table table-condensed']/thead/tr/th[3]" position="after">
                <th class="text-right">Analytic Account</th>
                <th class="text-right">Analytic Tags</th>
            </xpath>
            <xpath expr="//table[@class='table table-condensed']/tbody/tr/td[3]" position="after">
                <td class="text-right">testt1</td>
                <td class="text-right">testt2</td>
            </xpath>
        </template>

here is my pdf qweb report that has no effect of my work. 
https://i.stack.imgur.com/xdYhB.png