input: Write a function to list the contents of a specified directory using Python. The function should take the directory path as input and return a list of all items in that directory. If the directory does not exist, the function should return an empty list.
  
  assert list_directory_contents('C:\\path\\to\\directory')==['file1.txt', 'file2.txt', 'folder1']
  assert list_directory_contents('C:\\nonexistent\\directory')==[]
output: import os
  
  def list_directory_contents(directory_path):
      if not os.path.exists(directory_path):
          return []
      return os.listdir(directory_path)