How to make odoo sequence ?

sequence.py

class your_model_class_name (models.Model):
    _name = "your_model_name"

    @api.model
    def create(self, vals):
        if vals.get('seq', 'New') == 'New':
            vals['seq'] = self.env['ir.sequence'].next_by_code('example.seq') or '/'
        newId = super(your_model_class_name, self).create(vals)
        return newId

sequence.xml

<odoo>  
  <data noupdate="1">

      <record id="seq_id" model="ir.sequence">
          <field name="name">Sequence</field>
          <field name="code">example.seq</field>
          <field name="prefix">EX</field>
          <field name="padding">7</field>
      </record>

  </data> 
</odoo>