controller:

# -*- coding: utf-8 -*- from odoo import http from odoo import api, fields, models, SUPERUSER_ID, _ import re 
class callback(http.Controller): 
 _inherit = 'mail.message' 
# def __init__(self, pool): 
# self.pool = pool 
 @http.route('/callback/', auth='public') 
 def index(self, **kw): 
  self.send_mail_example() 
  return "Hello, world" 

Model:

# -*- coding: utf-8 -*- 
from odoo import http from odoo import api, fields, models, SUPERUSER_ID, _ import re 
class callback2(http.Controller): 
 _inherit = 'mail.message' 
 def send_mail_example(self, lead, kwargs): 
  """ Allow to be overrided """ 
  msg_id = False 
  email_to = ['darkink@mail.ru'] 
  ir_model_data = request.env['ir.model.data'] 
  email_template_obj = request.env['mail.template'] 
  crm_lead_obj = request.env['crm.lead'] 
  template_id = ir_model_data.get_object('bp_contact_snippet', 'email_template_website_message_lead') 
  if template_id.ids: 
    template = email_template_obj.sudo().browse(template_id.ids[0]) 
    crm_lead = crm_lead_obj.sudo().browse(lead) 
    if crm_lead: 
      values = template.sudo().generate_email(crm_lead.id) 
      message_contacts = request.env['website.message.contact'].sudo().search([]) 
      if message_contacts: 
        for message_contact in message_contacts: 
          email_to.append(message_contact.email) 
        values['email_to'] = ', '.join(email_to) 
        mail_mail_obj = request.env['mail.mail'] 
        msg_id = mail_mail_obj.sudo().create(values) 
  return msg_id 

in log:

self.send_mail_example() 
AttributeError: 'callback' object has no attribute 'send_mail_example' 

WHY?