Hello Shabeeh,

In PY :-
class custom_class(modules.Model):

     _name = 'custom.class'

    _inherit = ['mail.thread', 'ir.needaction_mixin']

In Xml:-

<record id="custom_class_form_view" model="ir.ui.view">

    <field name="name">custom.class.form.view</field>

     <field name="model">custom.class</field>

    <field name="arch" type="xml">

        <form string="Custom Class">

              <sheet>

             <!-- Code for Form View -->
    
              </sheet>

            <div class="oe_chatter">

                <field name="message_follower_ids" widget="mail_followers" groups="base.group_user"/>

                <field name="message_ids" widget="mail_thread"/>

            </div>

        </form>

    </field>

</record>

Thanks,