input: Write a function to list the contents of a directory in Python. The function should return a list of all items in the directory. If the directory is empty, the function should return an empty list.
  
  assert list_directory_contents("my_directory")==["file1.txt", "file2.txt", "subdir"]
  assert list_directory_contents("empty_directory")==[]
  assert list_directory_contents("non_existent_directory")==[]
output: import os
  
  def list_directory_contents(directory):
      if not os.path.exists(directory):
          return []
      return os.listdir(directory)