input: Write a function to list the contents of a given directory. The function should take the directory path as an input and return a list of its contents. If the directory is empty, return an empty list.
  assert list_directory_contents("C:/Users/user")==['Documents', 'Pictures', 'Downloads', 'Videos']
  assert list_directory_contents("C:/EmptyDir")==[]
  assert list_directory_contents("C:/NonExistentDir")==[]
output: import os
  
  def list_directory_contents(directory_path):
      if not os.path.exists(directory_path):
          return []
      return os.listdir(directory_path)