How to add css files to a custom module in Odoo?

How can I add css files to my custom module to change xml views? I found this post but the solution is not working.

I want modify all the elements from my module, such as forms, lists, inputs, etc.

1. You must create the css file in this route: /module_name/static/src/css/module_name.css. Example of file:

    .openerp .classname{
        margin: 12px 0px 12px 0px;
    }
   

2. Create the file /module_name/views/module_name.xml with this content:

    <?xml version="1.0"?>
    <openerp>
        <data>
            <template id="assets_backend" name="module_name assets" inherit_id="web.assets_backend">
                <xpath expr="." position="inside">
                    <link rel="stylesheet" href="/module_name/static/src/css/module_name.css"/>
                </xpath>
            </template>
        </data>     
    </openerp>
   

3. Add the xml file to your __openerp.__py

    'data': [
        'views/module_name.xml',
    ],
   

4. Add the class to the elements in the view

    <div class="classname">                            
        <field name="field_name" class="other_class"/>
    </div>