the compute Method will not be called when opening a custom wizard:

class x_dummy_createwizardClose(models.TransientModel):
    _name = 'x_dummy.createbeleg_close_wizard'
    description = fields.Char(string="Beschreibung", required=True)
    betrag_ist = fields.Float(string="IST-Stand", required=True)
    betrag_soll = fields.Float(string="Soll-Stand", compute='_compute_betrag_soll', required=True)

    @api.one
    def _compute_betrag_soll(self):
        #some logic here....
        self.betrag_soll = 20    # TESTING

but the Method _compute_betrag_soll will never be called
The Action vor opening the wizard looks as follows:

   <act_window id="launch_session_wizard_closer"
               name="create Close-Entry"
               src_model="x_dummy.dummy"
view_type="form"
               res_model="x_dummy.createbeleg_close_wizard"
               view_mode="form"
               target="new"
               key2="client_action_multi"/>