Your tree view can only show fields in a model, but for you to show the data from another model in your tree view, you can create a field and relate the new field to the data you want to get:

many_two_one_field = fields.Many2one('res.partner')
new_field = fields.Char(related='many_two_one_field.data_field')

The above shows there is a connecting field in your current model with the field you want to get that from; many_two_one_field

Regards