$10.$ Add Test Cases for before$\_$space

Reread the specification for before$\_$space, paying close attention to the precondition. Create test cases for this function and add them to the test procedure test$\_$before$\_$space in testcurrency.py$.$ Remember, to implement a test case:

Call the function on a sample input of your choice.

Store the returned result as a variable.

Compare the result with the expected output using assert$\_$equals in introcs.