adding exercises and part2 slides

exercises/Exercise 2a Local imports.md

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+## Exercise 2a: Local importing
+
+#### Goal
+
+Retrival practice in "basic" importing.
+
+#### Preparation
+
+(none)
+
+#### Tasks
+
+0. Create a file in the `src/` folder called `make_potion.py` and copy the code below
+   into it.
+
+```python
+# ADD IMPORT STATEMENTS HERE!
+
+
+def make_example_potion(student_name="ASPP student"):
+    my_potion = potion_class.Potion(student_name=student_name)
+    # Set up your old kettle and light an eternal flame underneath it.
+    my_potion.setup(container=containers.old_kettle)
+    # Simmer for 5 hours.
+    cooking.simmer(my_potion, duration=5)
+    print(f"You successfully ran make_example_potion, {student_name}, well done :).")
+    return my_potion
+
+
+my_name = 'ASPP student'
+my_potion = make_example_potion(student_name=my_name)
+```
+
+1. Figure out what import statements are missing, either by visual inspection or
+   by running the code and seeing what dies. Add the missing import statements at
+   the top of the file. You may need to inspect the files in `src/brewing/`.
+
+2. Run `make_potion.py`. Did it work?

exercises/Exercise 2b Unprotected code.md

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+## Exercise 2a: Unprotected code
+
+#### Goal
+
+Investigate what happens when importing from modules with "unprotected" code.
+
+#### Preparation
+
+(none)
+
+#### Tasks
+
+0. Create a file in the `src/` folder called `main.py`.
+
+1. Add a line in `main.py` that imports the `make_example_potion` function from
+   `make_potion.py`.
+
+2. **BEFORE YOU EXECUTE THE FILE**. Discuss with your partner what you think will
+   happen when you run `main.py`.
+
+3. Run `main.py`. Does your prediction match reality?
+
+4. (optional, for those who know) Discuss with your partner:
+    * Why did this behaviour occur?
+    * Why is it not good?
+    * What can you do to "fix" the behaviour?