In purchase requisition model, I have created an extra button.I want to give group privilege to that button. So that I gave

<button name="tender_techteam_approval" states="manager_approval" string="TechTeam Approval"  type="object" class="oe_highlight" groups="material.group_tech_team"/>

But its not working. Then I tried with attrribute like below,again it doesn't working.

attrs="{'invisib le': [('user_id.groups_id.name':'group_tech_team')]}"

user_id = many2one field of res.users

groups_id = many2many field  of res.groups and name is a field in res.groups. How can I work this below attribute or any other option to give privilege to that button ?