When I try to extend the view of my parent view an error: "Model not found: todo.task" raise here is my code:

my parent Model:

# -*- coding: utf-8 -*-
from odoo import models, fields, api


class TodoTask(models.Model):
    _name= 'todo.task'
    _description = 'To-do Task'
    name= fields.Char('Description', required=True)
    is_done= fields.Boolean('Done?')
    active = fields.Boolean('Active?', default=True)

    @api.multi
    def do_toggle_done(self):
        for task in self:
            task.is_done= not task.is_done
            return True



    @api.model
    def do_clear_done(self):
        dones = self.search([('is_done','=',True)])
        dones.write({'active':False})
        return True

the extending Model:

# -*- coding: utf-8 -*-

from odoo import models, fields,api
from odoo.exceptions import ValidationError

class TodoTask(models.Model):

    _inherit = 'todo.task'
    user_id= fields.Many2one('res.users', 'Responsible')
    date_deadline= fields.Date('Deadline')

    @api.multi
    def do_clear_done(self):
        domain = [('is_done','=',True), '|', ('user_id', '=', self.env.uid),('user_id','=',False)]
        dones= self.search(domain)
        dones.write({'active': False})
        return True

    @api.multi
    def do_toggle_done(self):
        for task in self:
            if task.user_id != self.env.user:
                raise  ValidationError(
                    'Only the responsible can do this !'
                )
        return super(TodoTask, self).do_toggle_done()

my parent view:

<odoo>

  <record id="view_form_todo_task" model="ir.ui.view">
    <field name="name"> To-do Task Form</field>
    <field name ="model">todo.task</field>
    <field name="arch" type="xml">


      <form >
        <header>

          <button name ="do_toggle_done" type="object"
                  string="Toggle Done"
                  class="oe_highlight" />

          <button name ="do_clear_done"
                  type="object"
                  string="Clear All Done" />

        </header>

        <sheet>

           <group name="group_top">

             <group name="group-left">
               <field name="name"/>
             </group>

             <group name="group_right">
               <field name="is_done"/>
               <field name="active" readonly="1"/>
             </group>

        </group>

        </sheet>
      </form>


    </field>

  </record>


    <record id="view_tree_todo_task" model="ir.ui.view">
       <field name="name">To-do Task Tree</field>
        <field name="model">todo.task</field>
        <field name="arch" type="xml">

            <tree colors="decoration-muted:is_done==True">
                <field name="name"/>
                <field name="is_done"/>
            </tree>

        </field>
    </record>



  <record id="view_filter_todo_task" model="ir.ui.view">
    <field name="name">To-do Task Filter</field>
    <field name="model">todo.task</field>
    <field name="arch" type="xml">

    <search>
      <field name="name"/>

      <filter string="Not Done"
             domain="[('is_done','=',False)]"/>

      <filter string="Done"
             domain="[('is_done','!=',False)]"/>

    </search>
    </field>
  </record>


</odoo>

the extending view:


<odoo>


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

        <field name="name">
            Todo Task form -User extension
        </field>

        <field name="model">
            todo.task
        </field>

        <field name="inherit_id"
               ref="todo_app.view_form_todo_task"/>

        <field name="arch" type="xml">

            <field name="name" position="after">

                <field name="user_id"></field>

                <field name="is_done" position="before">

                    <field name="date_deadline"/>
                </field>

                <field name="active" position="attributes">
                    <attribute name="invisible">1</attribute>

                </field>

            </field>

        </field>


    </record>


    <record id="view_tree_todo_task_inherited"
            model="ir.ui.view">
        <field name="name">
            Todo Task tree - User extension
        </field>

        <field name="model">
            todo.task
        </field>

        <field name="inherit_id"
               ref="todo_app.view_tree_todo_task"/>

        <field name="arch" type="xml">

            <field name="name" position="after">
                <field name="user_id"/>
            </field>


        </field>

    </record>


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

        <field name="name">
            Todo Task tree - User extension
        </field>

        <field name="model">
            todo.task
        </field>

        <field name="inherited_id"
               ref="todo_app.view_filter_todo_task"/>

        <field name="arch" type="xml">

            <field name="name" position="after">

                <field name="user_id"/>
                <filter name="filter_my_tasks" string="My Tasks"
                        domain="[('user_id','in',[uid,False])]"/>

                <filter name="filter_not_assigned" string="Not Assigned"
                        domain="[('user_id','=',False)]"/>

            </field>



        </field>



    </record>



</odoo>