<record model="ir.actions.server" id="make_it_done">
    <field name="name">Make it done</field>
    <field name="condition">True</field>
    <field name="model_id" ref="model_todo_task"/>
    <field name="type">ir.actions.server</field>
    <field name="binding_model_id" ref="model_todo_task" />
    <field name="code">
        action = self.make_it_done()
    </field>
</record>

from odoo import api,fields, models
from odoo.addons.base.res.res_request import referenceable_models
from odoo.exceptions import ValidationError

class TodoTask(models.Model):

def make_it_done(self):
    print('Success!!')