How I achieve something like by using following piece of code:

@api.model
def fields_view_get(self, view_id=None, view_type='form', toolbar=False, submenu=False):
    if view_type == 'form':
        res['arch'] = self.fields_view_get_address(res['arch'])
        record = self.env['crm.lead'].browse(self._context.get('params').get('id'))
        # restrict modification and deletion of child ids
        if record.parent_id:
            res['arch'] = res['arch'][:6] + 'edit="false" delete="false" ' + res['arch'][6:]
        elif record.stage_id.id == 4:  # restrict edition of Purchased Lead
            res['arch'] = res['arch'][:6] + 'edit="false" ' + res['arch'][6:]

    return res