How to use the ipyleaflet.leaflet.Layer function in ipyleaflet

self._add_unit(name, factor, decimals)

    def _add_unit(self, name, factor, decimals):
        self._custom_units_dict[name] = {
            'factor': factor,
            'display': name,
            'decimals': decimals
        }
        self._custom_units = dict(**self._custom_units_dict)


class SplitMapControl(Control):
    _view_name = Unicode('LeafletSplitMapControlView').tag(sync=True)
    _model_name = Unicode('LeafletSplitMapControlModel').tag(sync=True)

    left_layer = Union((Instance(Layer), List(Instance(Layer)))).tag(sync=True, **widget_serialization)
    right_layer = Union((Instance(Layer), List(Instance(Layer)))).tag(sync=True, **widget_serialization)

    @default('left_layer')
    def _default_left_layer(self):
        return TileLayer()

    @default('right_layer')
    def _default_right_layer(self):
        return TileLayer()

    def __init__(self, **kwargs):
        super(SplitMapControl, self).__init__(**kwargs)
        self.on_msg(self._handle_leaflet_event)

    def _handle_leaflet_event(self, _, content, buffers):
        if content.get('event', '') == 'dividermove':

self._dblclick_callbacks.register_callback(callback, remove=remove)

    def on_mousedown(self, callback, remove=False):
        self._mousedown_callbacks.register_callback(callback, remove=remove)

    def on_mouseup(self, callback, remove=False):
        self._mouseup_callbacks.register_callback(callback, remove=remove)

    def on_mouseover(self, callback, remove=False):
        self._mouseover_callbacks.register_callback(callback, remove=remove)

    def on_mouseout(self, callback, remove=False):
        self._mouseout_callbacks.register_callback(callback, remove=remove)


class UILayer(Layer):
    _view_name = Unicode('LeafletUILayerView').tag(sync=True)
    _model_name = Unicode('LeafletUILayerModel').tag(sync=True)


class Icon(UILayer):
    _view_name = Unicode('LeafletIconView').tag(sync=True)
    _model_name = Unicode('LeafletIconModel').tag(sync=True)

    icon_url = Unicode('').tag(sync=True, o=True)
    shadow_url = Unicode(None, allow_none=True).tag(sync=True, o=True)
    icon_size = Tuple((10, 10), allow_none=True).tag(sync=True, o=True)
    shadow_size = Tuple((10, 10), allow_none=True).tag(sync=True, o=True)
    icon_anchor = Tuple((0, 0), allow_none=True).tag(sync=True, o=True)
    shadow_anchor = Tuple((0, 0), allow_none=True).tag(sync=True, o=True)
    popup_anchor = Tuple((0, 0), allow_none=True).tag(sync=True, o=True)

location = List(def_loc).tag(sync=True)

    # Options
    radius = Int(10, help='radius of circle in pixels').tag(sync=True, o=True)


class Circle(CircleMarker):
    _view_name = Unicode('LeafletCircleView').tag(sync=True)
    _model_name = Unicode('LeafletCircleModel').tag(sync=True)

    # Options
    radius = Int(1000, help='radius of circle in meters').tag(sync=True, o=True)


class MarkerCluster(Layer):
    _view_name = Unicode('LeafletMarkerClusterView').tag(sync=True)
    _model_name = Unicode('LeafletMarkerClusterModel').tag(sync=True)

    markers = Tuple().tag(trait=Instance(Marker), sync=True, **widget_serialization)


class LayerGroup(Layer):
    _view_name = Unicode('LeafletLayerGroupView').tag(sync=True)
    _model_name = Unicode('LeafletLayerGroupModel').tag(sync=True)

    layers = Tuple().tag(trait=Instance(Layer), sync=True, **widget_serialization)

    _layer_ids = List()

    @validate('layers')
    def _validate_layers(self, proposal):

# Options
    min_width = Int(50).tag(sync=True, o=True)
    max_width = Int(300).tag(sync=True, o=True)
    max_height = Int(default_value=None, allow_none=True).tag(sync=True, o=True)
    auto_pan = Bool(True).tag(sync=True, o=True)
    auto_pan_padding_top_left = List(allow_none=True, default_value=None).tag(sync=True, o=True)
    auto_pan_padding_bottom_right = List(allow_none=True, default_value=None).tag(sync=True, o=True)
    auto_pan_padding = List([5, 5]).tag(sync=True, o=True)
    keep_in_view = Bool(False).tag(sync=True, o=True)
    close_button = Bool(True).tag(sync=True, o=True)
    auto_close = Bool(True).tag(sync=True, o=True)
    close_on_escape_key = Bool(True).tag(sync=True, o=True)
    class_name = Unicode('').tag(sync=True, o=True)


class RasterLayer(Layer):
    _view_name = Unicode('LeafletRasterLayerView').tag(sync=True)
    _model_name = Unicode('LeafletRasterLayerModel').tag(sync=True)

    opacity = Float(1.0, min=0.0, max=1.0).tag(sync=True)
    visible = Bool(True).tag(sync=True)


class TileLayer(RasterLayer):
    _view_name = Unicode('LeafletTileLayerView').tag(sync=True)
    _model_name = Unicode('LeafletTileLayerModel').tag(sync=True)

    bottom = Bool(True).tag(sync=True)
    url = Unicode('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png').tag(sync=True)
    min_zoom = Int(0).tag(sync=True, o=True)
    max_zoom = Int(18).tag(sync=True, o=True)
    min_native_zoom = Int(0).tag(sync=True, o=True)

def __iadd__(self, item):
        if isinstance(item, Layer):
            self.add_layer(item)
        elif isinstance(item, Control):
            self.add_control(item)
        return self

# Options
    attribution = Unicode().tag(sync=True, o=True)


class VideoOverlay(RasterLayer):
    _view_name = Unicode('LeafletVideoOverlayView').tag(sync=True)
    _model_name = Unicode('LeafletVideoOverlayModel').tag(sync=True)

    url = Unicode().tag(sync=True)
    bounds = List([def_loc, def_loc], help='SW and NE corners of the image').tag(sync=True)

    # Options
    attribution = Unicode().tag(sync=True, o=True)


class Velocity(Layer):
    _view_name = Unicode('LeafletVelocityView').tag(sync=True)
    _model_name = Unicode('LeafletVelocityModel').tag(sync=True)

    zonal_speed = Unicode('', help='Name of the zonal speed in the dataset')
    meridional_speed = Unicode('', help='Name of the meridional speed in the dataset')
    latitude_dimension = Unicode('latitude', help='Name of the latitude dimension in the dataset')
    longitude_dimension = Unicode('longitude', help='Name of the longitude dimension in the dataset')
    units = Unicode(None, allow_none=True)

    data = Dataset().tag(dtype=None, sync=True, to_json=ds_x_to_json)

    # Options
    display_values = Bool(True).tag(sync=True, o=True)
    display_options = Dict({
        'velocityType': 'Global Wind',
        'position': 'bottomleft',

class Heatmap(RasterLayer):
    _view_name = Unicode('LeafletHeatmapView').tag(sync=True)
    _model_name = Unicode('LeafletHeatmapModel').tag(sync=True)

    locations = List().tag(sync=True)

    # Options
    min_opacity = Float(0.05).tag(sync=True, o=True)
    max_zoom = Int(18).tag(sync=True, o=True)
    max = Float(1.0).tag(sync=True, o=True)
    radius = Float(25.0).tag(sync=True, o=True)
    blur = Float(15.0).tag(sync=True, o=True)
    gradient = Dict({0.4: 'blue', 0.6: 'cyan', 0.7: 'lime', 0.8: 'yellow', 1.0: 'red'}).tag(sync=True, o=True)


class VectorLayer(Layer):
    _view_name = Unicode('LeafletVectorLayerView').tag(sync=True)
    _model_name = Unicode('LeafletVectorLayerModel').tag(sync=True)


class Path(VectorLayer):
    _view_name = Unicode('LeafletPathView').tag(sync=True)
    _model_name = Unicode('LeafletPathModel').tag(sync=True)

    # Options
    stroke = Bool(True).tag(sync=True, o=True)
    color = Color('#0033FF').tag(sync=True, o=True)
    weight = Int(5).tag(sync=True, o=True)
    fill = Bool(True).tag(sync=True, o=True)
    fill_color = Color('#0033FF').tag(sync=True, o=True)
    fill_opacity = Float(0.2).tag(sync=True, o=True)
    dash_array = Unicode(allow_none=True, default_value=None).tag(sync=True, o=True)

def __init__(self, **kwargs):
        super(Layer, self).__init__(**kwargs)
        self.on_msg(self._handle_mouse_events)

class Circle(CircleMarker):
    _view_name = Unicode('LeafletCircleView').tag(sync=True)
    _model_name = Unicode('LeafletCircleModel').tag(sync=True)

    # Options
    radius = Int(1000, help='radius of circle in meters').tag(sync=True, o=True)


class MarkerCluster(Layer):
    _view_name = Unicode('LeafletMarkerClusterView').tag(sync=True)
    _model_name = Unicode('LeafletMarkerClusterModel').tag(sync=True)

    markers = Tuple().tag(trait=Instance(Marker), sync=True, **widget_serialization)


class LayerGroup(Layer):
    _view_name = Unicode('LeafletLayerGroupView').tag(sync=True)
    _model_name = Unicode('LeafletLayerGroupModel').tag(sync=True)

    layers = Tuple().tag(trait=Instance(Layer), sync=True, **widget_serialization)

    _layer_ids = List()

    @validate('layers')
    def _validate_layers(self, proposal):
        '''Validate layers list.

        Makes sure only one instance of any given layer can exist in the
        layers list.
        '''
        self._layer_ids = [l.model_id for l in proposal.value]
        if len(set(self._layer_ids)) != len(self._layer_ids):