In products, in product.template model I want to change the field name of field 'type'

The code is

'type': fields.selection([('consu', 'Consumable'),('service','Service')], 'Product Type', required=True, help="Consumable are product where you don't manage stock, a service is a non-material product provided by a company or an individual.")

Here the product name is 'Product Type' I want to change this as 'Material type'.

I tried changing it

'type': fields.selection([('consu', 'Consumable'),('service','Service')], 'Material Type', required=True, help="Consumable are product where you don't manage stock, a service is a non-material product provided by a company or an individual.")

I have restarted server and I have also upgraded the product module. But the name of the field was not changed. I tried with another field it changes. How to change the name of this field ('type')?

I have an another doubt in the same field. It is a selection field. In the code it has two selections

'type': fields.selection([('consu', 'Consumable'),('service','Service')], 'Product Type', required=True, help="Consumable are product where you don't manage stock, a service is a non-material product provided by a company or an individual.")

Hence in the selection it must show Consumable and Service. But it shows an extra selection Stockable Product.

How is this possible?

Thanks.