How to use the kivy.properties.ObjectProperty function in Kivy

elif mode == 'wstone':
            board.input_mode = 'wstone'
        elif mode == 'estone':
            board.input_mode = 'estone'
    def on_board_to_play(self,*args):
        toplay = self.board_to_play
        if toplay == 'w' and self.bplay_button.state == 'down':
            self.wplay_button.state = 'down'
            self.bplay_button.state = 'normal'
        elif toplay == 'b' and self.wplay_button.state == 'down':
            self.bplay_button.state = 'down'
            self.wplay_button.state = 'normal'
        

class CommentInput(BoxLayout):
    board = ObjectProperty(None)
    popup = ObjectProperty(None)
    comment = StringProperty('')

class SaveQuery(BoxLayout):
    collections_list = ObjectProperty(None,allownone=True)
    board = ObjectProperty(None,allownone=True)
    sgf_model = ObjectProperty(None,allownone=True)

def get_collectioninfo_from_dir(row_index,dirn):
    sgfs = glob(dirn + '/*.sgf')
    colname = dirn.split('/')[-1]
    return {'colname': colname, 'coldir': dirn, 'numentries': len(sgfs)}

class MySpinnerOption(SpinnerOption):
    pass

def on_drive_selected(self, *args):
        """ Changes the current drive letter in Windows OS.
        """
        try:
            selected_drive = args[0].text
        except IndexError:
            return
        self.filechooser.path = selected_drive


# noinspection PyIncorrectDocstring,PyArgumentList
class SaveDialog(BoxLayout):
    """ 'Save File' popup dialog.
    """
    save = ObjectProperty(None)
    cancel = ObjectProperty(None)
    file_types = ListProperty(['*.*'])
    text_input = ObjectProperty(None)

    def __init__(self, **kwargs):
        super(SaveDialog, self).__init__(**kwargs)
        self.filechooser.path = './'
        self.create_drives()

    def create_drives(self):
        """ Creates the Drive list in Windows OS.
        """
        for i in get_win_drives():
            btn = DarkButton(text=i)
            btn.bind(on_press=self.on_drive_selected)
            self.ids.drives_list.add_widget(btn)

class Particle(object):
    x, y, rotation, current_time = 0, 0, 0, 0
    scale, total_time = 1.0, 1.0
    color = [1.0, 1.0, 1.0, 1.0]
    color_delta = [0.0, 0.0, 0.0, 0.0]
    start_x, start_y, velocity_x, velocity_y = 0, 0, 0, 0
    radial_acceleration, tangent_acceleration = 0, 0
    emit_radius, emit_radius_delta = 0, 0
    emit_rotation, emit_rotation_delta = 0, 0
    rotation_delta, scale_delta = 0, 0


class ParticleSystem(Widget):
    max_num_particles = NumericProperty(200)
    life_span = NumericProperty(2)
    texture = ObjectProperty(None)
    life_span_variance = NumericProperty(0)
    start_size = NumericProperty(16)
    start_size_variance = NumericProperty(0)
    end_size = NumericProperty(16)
    end_size_variance = NumericProperty(0)
    emit_angle = NumericProperty(0)
    emit_angle_variance = NumericProperty(0)
    start_rotation = NumericProperty(0)
    start_rotation_variance = NumericProperty(0)
    end_rotation = NumericProperty(0)
    end_rotation_variance = NumericProperty(0)
    emitter_x_variance = NumericProperty(100)
    emitter_y_variance = NumericProperty(100)
    gravity_x = NumericProperty(0)
    gravity_y = NumericProperty(0)
    speed = NumericProperty(0)

class Ball(Widget):

    velocity_x = NumericProperty(0)
    velocity_y = NumericProperty(0)
    h = NumericProperty(0)
    velocity = ReferenceListProperty(velocity_x, velocity_y)

    def move(self):
        self.pos = Vector(*self.velocity) + self.pos


class PyobjusGame(Widget):

    ball = ObjectProperty(None)
    screen = ObjectProperty(autoclass('UIScreen').mainScreen())
    accelerometer = Accelerometer()

    sensitivity = ObjectProperty(50)
    br_slider = ObjectProperty(None)

    def __init__(self, *args, **kwargs):
        super(PyobjusGame, self).__init__()
        self.accelerometer.start()

    def __dealloc__(self, *args, **kwargs):
        # self.bridge.stopAccelerometer()
        self.accelerometer.stop()
        super(PyobjusGame, self).__dealloc__()

    def reset_ball_pos(self):
        self.ball.pos = self.width / 2, self.height / 2

class EffectWidget(RelativeLayout):
    '''
    Widget with the ability to apply a series of graphical effects to
    its children. See the module documentation for more information on
    setting effects and creating your own.
    '''

    background_color = ListProperty((0, 0, 0, 0))
    '''This defines the background color to be used for the fbo in the
    EffectWidget.

    :attr:`background_color` is a :class:`ListProperty` defaults to
    (0, 0, 0, 0)
    '''

    texture = ObjectProperty(None)
    '''The output texture of the final :class:`~kivy.graphics.Fbo` after
    all effects have been applied.

    texture is an :class:`~kivy.properties.ObjectProperty` and defaults
    to None.
    '''

    effects = ListProperty([])
    '''List of all the effects to be applied. These should all be
    instances or subclasses of :class:`EffectBase`.

    effects is a :class:`ListProperty` and defaults to [].
    '''

    fbo_list = ListProperty([])
    '''(internal) List of all the fbos that are being used to apply

from kivy.uix.widget import Widget
from kivy.properties import (StringProperty, ListProperty, NumericProperty, DictProperty, 
BooleanProperty, ObjectProperty)
from kivy.clock import Clock
import math


class GameSystem(Widget):
    system_id = StringProperty('default_id')
    updateable = BooleanProperty(False)
    renderable = BooleanProperty(False)
    paused = BooleanProperty(False)
    active = BooleanProperty(True)
    gameworld = ObjectProperty(None)
    viewport = StringProperty('default_gameview')

    def __init__(self, **kwargs):
        super(GameSystem, self).__init__(**kwargs)
        self.entity_ids = list()

    def update(self, dt):
        pass

    def draw_entity(self, entity_id):
        pass

    def generate_component_data(self, entity_component_dict):
        #this is the load function
        return entity_component_dict

def _deserialize(self, **kwargs):
        for key, data in kwargs.items():
            obj = getattr(self, key)
            obj.instance_from_json(data)



class RTLSDRScannerApp(App):
    def build(self):
        return RootWidget()
    def on_action_button_release(self, btn):
        btn.parent.parent.dismiss()
        Action.trigger_by_name(btn.action, self)

class PlotContainer(FloatLayout, JSONMixin):
    spectrum_graph = ObjectProperty(None)
    def add_plot(self, **kwargs):
        fn = kwargs.pop('filename', None)
        if fn is not None:
            kwargs.setdefault('name', os.path.basename(fn))
        plot = self.spectrum_graph.add_plot(**kwargs)
        self.tool_panel.add_plot(plot)
        return plot
    def _serialize(self):
        d = {'spectrum_graph':self.spectrum_graph._serialize()}
        return d
    def _deserialize(self, **kwargs):
        data = kwargs.get('spectrum_graph')
        self.spectrum_graph.instance_from_json(data)

class MessageDialog(BoxLayout):
    message = StringProperty()

class InfoPopup(BoxLayout):
    cancel = ObjectProperty(None)


class MouseOverLabel(Button):
    pass


class RevConcDialog(BoxLayout):
    cancel = ObjectProperty(None)


class InputList(BoxLayout):
    cancel = ObjectProperty(None)


class BookmarkLabel(Label):
    pass


class SideLabel(Label):
    pass


class PathLabel(Label):
    pass


class PathText(AutoCompTextInput):
    pass