Hi, I want to add a unique constraint for a specific field but i have an error of ValidateError
Une erreur est apparue lors de la validation du/des champ(s) arch: Invalid XML for View Architecture!
my file.py
enter code here_columns = {
    'sequence': fields.integer('Sequence', help="Used to order the note stages"),
    'cne':fields.char('Matricule', size=64,required=True),
}
enter code here
_sql_constraints = [('student_state_name_unique','unique(cne)', 'State name already exists')]
myfile.xml
<?xml version="1.0" encoding="utf-8"?>
<openerp>
<data> 
<record model="ir.ui.view" id="view_school_student_form">
        <field name="name">student.form</field>
        <field name="model">student</field>
        <field name="type">form</field>
        <field name="arch" type="xml">
            <form string="Information Eleve" version="7.0">
                <sheet>
                <notebook colspan="6"> 
                 <page string="Informations ">
                  <separator string="Informations administratives" colspan="6"/>
                      <group col="6" colspan="6">
                        <field name="sequence" widget="handler" invisible="1"/>
