_inherit = 'sale.order'
	​proposal_id = fields.Many2one(
        'proposals',
        string='Proposal',
        readonly=True,
        states={'draft': [('readonly', False)]}
    )

I'm trying to understand what is states​ in Many2one field. Proposal​ is a class module that I made. There is state​ field in it but since the flow is to create the proposal first then automatically create sale.order​, why there is states​ in Many2one field? I try to remove it and nothing change. I want to know what states​ do here