input: Write a function to list the contents of a directory using Python. The function should take no arguments and return a list of the directory's contents.
  assert list_directory_contents()==['file1.txt', 'folder1', 'file2.txt']
  assert list_directory_contents()==['file1.txt', 'file3.txt']
  assert list_directory_contents()==[]
output: def list_directory_contents():
      import os
      return os.listdir()