in a model i defined a company_id this way:

company_id = fields.Many2one(
    'res.company',
    'Company',
    default=lambda self: self.env.user.company_id 
    )

In a new document edit form the company id is correctly selected, but when I click on "company id" selection, I get this error:

Uncaught Error: AttributeError: object has no attribute 'company_id'

The "self" object appears to be empty, when logged.

I copied the definition of company_id from one of many core or OCA modules that uses it.

Does it rely on context?

And how could I get the id of the current user and is company_id?