new_contents: # This lesson teaches you how to define a Python method. Try running the tests for this file before doing anything!
  
  # Here's a python script you can use to run your tests from the top level directory of this project
  # `python -m unittest -vf tests.test_lesson_0_hello_world`
  # That command looks like a lot at first. Let's break it down.
  
  
  # `python` indicates that you want to run a python file
  # -m tells python to run the module (tests.test_lesson_x) as a script
  # unittest tells python that we're running unit tests on something
  # -vf is the combination of two options that I'll outline separately below:
  # -v encourages python to be as verbose as possible with its output
  # -f tells python to stop running the tests once it hits a failure. This is entirely optional, but I
  # want you to try running the tests one at a time, and fix each failure as it comes, rather than trying to
  # make all the tests pass at once. That way you get a feel for how to build some python functions one idea at a time
  # `tests.test_lesson_0_hello_world` is the specific module (composed of unit tests) that we're executing
  
  
  # What error did you get when you first ran it? 
  # Remember, errors are built to be **helpful**, not scary!
  
  # It should be an ImportError. This is Python telling you that it's unable to import the file `hello_world`
  
  # So your first step should be to create `hello_world.py` in the `lessons/lesson_0_hello_world` directory
  
  # Run the tests again. 
  
  import unittest
  
  from lessons.lesson_0_hello_world import hello_world
  
  class HelloWorldTestClass(unittest.TestCase):
      def test_hello_function_exists(self):
          func = hello_world.hello_world
          self.assertIsNotNone(func)
  
      def test_hello_function_output(self):
      	greeting = hello_world.hello_world()
      	self.assertEqual(greeting, "Hello World!")
  
subject: Add test file for lesson 0.