How to use the kivy.clock.Clock.schedule_once function in Kivy

def create_display(self, width, height, name, bpp=24, **kwargs):
        self.displays[name] = MpfDisplay(width=width, height=height, bpp=bpp)

        Clock.schedule_once(self.display_created)

def _switch_picker(self, *a, **kw):
        noanim = "noanim" in kw
        if noanim:
            noanim = kw["noanim"]

        try:
            container = self.ids.picker_container
        except (AttributeError, NameError):
            Clock.schedule_once(lambda *a: self._switch_picker(noanim=noanim))

        if self.picker == "hours":
            picker = self._h_picker
            prevpicker = self._m_picker
        elif self.picker == "minutes":
            picker = self._m_picker
            prevpicker = self._h_picker

        if len(self._bound) > 0:
            prevpicker.unbind(selected=self.on_selected)
            self.unbind(**self._bound)
        picker.bind(selected=self.on_selected)
        self._bound = {"selector_color": picker.setter("selector_color"),
                       "color": picker.setter("color"),
                       "selector_alpha": picker.setter("selector_alpha")}
        self.bind(**self._bound)

		render.add_done_callback(lambda job:Clock.schedule_once(partial(self.on_render_finished,job),0.01))

def on_touch_up(self, touch):
        if touch.grab_current is not self:
            return
        touch.ungrab(self)
        self._num_touches -= 1
        if self._pinch_flag:
            if self._num_touches == 0:
                # user was pinching, and now both fingers are up. Return
                # to normal
                if self.sv_idx > touch.ud['orig_sv_idx']:
                    Clock.schedule_once(
                        self.inertial_incr_sv_idx,
                        (Clock.get_time() - touch.ud['orig_time']) /
                        (self.sv_idx - touch.ud['orig_sv_idx']))

                if self.sv_idx < touch.ud['orig_sv_idx']:
                    Clock.schedule_once(
                        self.inertial_decr_sv_idx,
                        (Clock.get_time() - touch.ud['orig_time']) /
                        (self.sv_idx - touch.ud['orig_sv_idx']))

                self._pinch_flag = False
                return
            else:
                # user was pinching, and at least one finger remains. We
                # don't want to treat the remaining fingers as touches
                return

def spawn_enemy_on_portal(self):
        if not self.tile_with_portal.actor:
            self.tile_with_portal.add_actor()
            Clock.schedule_once(self.add_actor_to_portal, 0.7)

def dismiss(self, *largs):
        '''Remove the dropdown widget from the window and detach it from
        the attached widget.
        '''
        Clock.schedule_once(self._real_dismiss, self.min_state_time)

def purchase(self, sku):
        # Really need to move these debug settings to a global 
        # settings file. Oh and they say that global settings files are bad.
        # Let's get to the bottom of it.
        if DEBUG:
            self.debug_sku = sku
            sku = 'android.test.purchased'
            if sku not in self.skus:
                self.skus.append(sku)
            Logger.warning('IAB is running in DEBUG mode and won\'t buy anything!')
        if self.purchase_requested is not None:
            self._toast('purchase already in progress')
            return False
        elif self.syncing:
            self.purchase_requested = sku
            Clock.schedule_once(self._fail, TIMEOUT)
            self._toast('will start purchase shortly')
            return True
        else:
            Logger.info('Purchasing ' + sku)
            if not self.setup_complete:
                self._toast('will start purchase shortly')
            else:
                self._toast('purchase started')
            self.purchase_requested = sku
            Clock.schedule_once(self._fail, TIMEOUT)
            self._process_purchase()
            return True

def export_finish(self):
        app = App.get_running_app()
        content = MessagePopup(text='Exporting Collage')
        if len(self.images) > 8:
            message = 'Exporting Collage, This May Take Several Minutes, Please Wait...'
        else:
            message = 'Exporting Collage, Please Wait...'
        self.popup = NormalPopup(title=message, content=content, size_hint=(None, None), size=(app.popup_x, app.button_scale * 4))
        self.popup.open()

        #Wait a cycle so the popup can display
        Clock.schedule_once(self.export_process)

def plotNextPoint(self, *args):
        point = self.listOfPointsToPlot[self.pointIndex]
        self.pointIndex = self.pointIndex + 1
        xValue = point[0]
        yValue = point[1]

        pointPlotted, distortedPoint = self.testPointGenerator.plotPoint(xValue, yValue)
        self.listOfPointsPlotted.append(pointPlotted)
        self.listOfDistortedPoints.append(distortedPoint)

        if self.pointIndex < len(self.listOfPointsToPlot):
            Clock.schedule_once(self.plotNextPoint)
        else:
            self.drawLines()