i have odoo 12 

i am creating a custom module and have a field 'assigned_to'

*.py

assigned_to = fields.Many2one('res.users', string='Assigned To')

i need to filter assigned_user with logged user

*.xml

<record id="bug_search_view" model="ir.ui.view">
    <field name="name">test.Search.View</field>
    <field name="model">test.test</field>
    <field name="arch" type="xml">
        <search string="Search Bugs">
            <field name="project_name" 

                   filter_domain="['|',('title_name', 'ilike',self), ('project_name', 'ilike', self)]"/>
            <field name="title_name"/>
            <field name="project_name"/>
            <separator/>
            00
            <filter string="Assigned to Me" name="assigned_to" domain="[('user_id', '=', uid)]" help="assigned to me"/>
        </search>
    </field>
</record>

I got an error

 raise ValueError("Invalid field %r in leaf %r" % (left, str(leaf)))
ValueError: Invalid field 'user_id' in leaf "<osv.ExtendedLeaf: ('user_id', '=', 2) on bugg__tracker_bugg__tracker (ctx: )>"

please help me to fix this issue.....