how to make a custom sequence in odoo with condition
def create(self, cr, uid, vals, context=None):
if vals.get('chalan')=='Chalan':
if vals.get('chalan_number','/')=='/':
vals['chalan_number'] = self.pool.get('ir.sequence').get(cr, uid, 'your_sequence_name') or '/'
return super(your_class_name,self).create(cr, uid, vals, context=context)