input: Write a python function to print a directory of a given folder.
  assert directoryListing('.') is None  # Should print the directory contents of the current folder
  assert directoryListing('..') is None  # Should print the directory contents of the parent folder
  assert directoryListing('/tmp') is None  # Should print the directory contents of the /tmp folder
output: def directoryListing(folder):
      import os
      for item in os.listdir(folder):
          print(item)