How to use _fields option in odoo 8
self._fields it will return the fields which are available in that model to a dictionary type 
model._fields[fieldname] will return the datatype of field as key and the field name with respective model as value
example self._fields['price_unit'] in sale.order.line will return
 Float: sale.order.line.price_unit
I am new to odoo.
Is anyone have tutorial of using _fields feature in odoo 8 ?
In odoo 8, _columns is deprecated.

A common pattern in OpenERP was to do Model fields introspection using _columns property. From 8.0 _columns is deprecated by _fields that contains list of consolidated fields instantiated using old or new API.

There is no clear documentation about _fields options.
Please give a right tutorial on this.