Nebula playout plugin examle (content alert)

import time
from nebula.plugins.playout import PlayoutPlugin, PlayoutPluginSlot


class Plugin(PlayoutPlugin):

    # Plugin info. Plugin name needs to be appended to the channels plugin list
    name = "content_alert"

    # Default CasparCG layer. Used by self.layer() method
    id_layer = 98

    # Slots are inuputs for the plugin. they will be displayed as widgets in
    # the Firefly plugin control UI. In this case, we want to be able to
    # manually hide the alert if something goes wrong. "action" type Slots
    # will be displayed as buttons.
    slots = [
        PlayoutPluginSlot(type="action", name="Hide")
    ]

    # Custom attribute holding the current parental guidance level
    current_level: int | None = None


    def on_change(self):
        # This method is called every time a new item starts playing
        # we wait a bit to make sure the item is actually playing
        time.sleep(0.2)

        # Then we check if the item has a parental guidance level
        if alert := self.current_item["content_alert/scheme"]:
            self.current_level = {
                "53.1.2": 12,
                "53.1.3": 15,
                "53.1.4": 18,
            }.get(alert)

            # If it does, we add two tasks to the plugin task list
            # The tasks will be executed in order, and will be repeated
            # until they return True. This allows us to wait for the
            # right moment to show or hide the alert.
            if self.current_level:
                self.tasks = [self.show, self.hide]
                return

        # If the item does not have a parental guidance level, we clear
        # the tasks list and hide the layer
        self.current_level = None
        self.tasks = []
        self.query(f"CLEAR {self.layer()}")

    def show(self):
        # This method is called by the first task in the task list
        # It will be called repeatedly until it returns True
        # Our goal is to show the alert after the item has been playing
        # for 5 seconds. We check the item position and return False
        # if it's too early.
        if self.position < 5:
            return False

        # If it's not too early, we show the alert and return True
        # to tell the task list that we're done, and that it can be
        # removed from the task list.
        self.query(f"PLAY {self.layer()} alert-{self.current_level} MIX 25")
        return True

    def hide(self):
        # This method is called by the second task in the task list
        # It will be called repeatedly until it returns True
        # Our goal is to hide the alert after the item has been playing
        # for 10 seconds. We check the item position and return False
        # if it's too early.
        if self.position < 10:
            return False

        # If it's not too early, we hide the alert and return True
        # to tell the task list that we're done, and that it can be
        # removed from the task list.
        self.query(f"PLAY {self.layer()} EMPTY MIX 25")
        return True

    def on_command(self, action, data):
        # This method is called when a Slot is triggered
        # We check if the Slot is the "Hide" Slot, and if it is,
        # we hide the alert.
        if action == "hide":
            self.query(f"PLAY {self.layer()} EMPTY")
        return True