class product_info(osv.osv):
    
    _name='product.info'
    
    
    _columns={
           'id':fields.integer('ID'),
            'product_id':fields.many2one('product.product','Name',required=True),
         'prod_category':fields.many2one('product.category','category'),
            'valid_from':fields.date('Valid From'),
            'valid_to':fields.date('Valid to'),
            
              }
    
    _sql_constraints=[('unique_product_id','unique(product_id)','Error! Product Name Already Exist!')]