I'm trying to upload multiple files from the Odoo website (student files), and then call a controller with method post to create a record and save the attachment.

this is my module  student.py

ref = fields.Char(string="Ref")
first_name = fields.Char(string="Firstname")
last_name = fields.Char(string="Lastname")
task_attachment = fields.Many2many(comodel_name="ir.attachment",
                            relation="m2m_ir_identity_card_rel",
                            column1="m2m_id",
                            column2="attachment_id",                            
                            string="Identity Card")
And this is my controller
@http.route('/create/webstudent', type="http", auth="user", website=True)
def create_webpatient(self, **kw):
    if request.httprequest.method == 'POST':
        new_task = request.env['university.student'].sudo().create(kw)
        if 'task_attachment' in request.params:
            attached_files = request.httprequest.files.getlist('task_attachment')
            for attachment in attached_files:
                attached_file = attachment.read()
                request.env['ir.attachment'].sudo().create({
                    'name': attachment.filename,
                    'res_model': 'university.student',
                    'res_id': new_task.id,
                    'type': 'binary',
                    'datas_fname': attachment.filename,
                    'datas': attached_file.encode('base64'),
                })

    return request.render("om_university.student_thanks", {})
When I click to the submit button this error show up :
ValueError: Wrong value for university.student.task_attachment: 
can anybody help me please!