input: Write a function to list the contents of a given directory path. If the directory does not exist, return an empty list. The function should take a single parameter which is the directory path.
  assert list_directory_contents(".")==os.listdir(".")
  assert list_directory_contents("non_existent_directory")==[]
  assert list_directory_contents("/")==os.listdir("/")
output: import os
  
  def list_directory_contents(path):
      if os.path.exists(path):
          return os.listdir(path)
      else:
          return []