warning to install optional dependencies

docs/source/examples.rst

@@ -40,6 +40,7 @@ up a job to send a message to that user after 30 seconds. The user can
 also cancel the timer by sending ``/unset``. To learn more about the
 ``JobQueue``, read `this wiki
 article <https://github.com/python-telegram-bot/python-telegram-bot/wiki/Extensions-%E2%80%93-JobQueue>`__.
+Note: To use JobQueue, you must install ptb via ``pip install python-telegram-bot[job-queue]``
 
 :any:`examples.conversationbot`
 -------------------------------
@@ -115,6 +116,7 @@ Don’t forget to enable and configure payments with
 `@BotFather <https://telegram.me/BotFather>`_. Check out this
 `guide <https://github.com/python-telegram-bot/python-telegram-bot/wiki/Telegram-Passport>`__
 on Telegram passports in PTB.
+Note: To use telegram passport, you must install ptb via ``pip install python-telegram-bot[passport]``
 
 :any:`examples.paymentbot`
 --------------------------
@@ -162,6 +164,7 @@ combination with ``telegram.ext.Application``.
 
 This example showcases how PTBs “arbitrary callback data” feature can be
 used.
+Note: To use arbitrary callback data, you must install ptb via ``pip install python-telegram-bot[callback-data]``
 
 Pure API
 --------

examples/arbitrarycallbackdatabot.py

@@ -6,6 +6,9 @@
 
 For detailed info on arbitrary callback data, see the wiki page at
 https://github.com/python-telegram-bot/python-telegram-bot/wiki/Arbitrary-callback_data
+
+Note:
+To use arbitrary callback data, you must install ptb via `pip install python-telegram-bot[callback-data]`
 """
 import logging
 from typing import List, Tuple, cast

examples/passportbot.py

@@ -10,6 +10,8 @@
 See https://github.com/python-telegram-bot/python-telegram-bot/wiki/Telegram-Passport
  for how to use Telegram Passport properly with python-telegram-bot.
 
+Note:
+To use telegram passport, you must install PTB via `pip install python-telegram-bot[passport]`
 """
 import logging
 from pathlib import Path

examples/timerbot.py

@@ -16,6 +16,9 @@
 Basic Alarm Bot example, sends a message after a set time.
 Press Ctrl-C on the command line or send a signal to the process to stop the
 bot.
+
+Note:
+To use arbitrary callback data you must install ptb via `pip install python-telegram-bot[callback-data]`
 """
 
 import logging

telegram/ext/_callbackcontext.py

@@ -22,6 +22,7 @@
 from telegram._callbackquery import CallbackQuery
 from telegram._update import Update
 from telegram.ext._extbot import ExtBot
+from telegram._utils.warnings import warn
 from telegram.ext._utils.types import BD, BT, CD, UD
 
 if TYPE_CHECKING:
@@ -389,6 +390,11 @@ def job_queue(self) -> Optional["JobQueue"]:
         .. seealso:: `Job Queue <https://github.com/python-telegram-bot/
             python-telegram-bot/wiki/Extensions-%E2%80%93-JobQueue>`_
         """
+        if self._application.job_queue is None:
+            warn(
+                "No `JobQueue` Set up. To use `JobQueue`, you must install PTB via"
+                "`pip install python-telegram-bot[job_queue]`."
+            )
         return self._application.job_queue
 
     @property