input: Write a function to list the contents of a specified directory. The function should take the path of the directory as input and return a list of its contents. If the directory does not exist, the function should return an empty list.
  assert list_directory_contents("/path/to/valid/directory")==["file1.txt", "file2.png", "folder1"]
  assert list_directory_contents("/path/to/nonexistent/directory")==[]
  assert list_directory_contents("")==[]
output: import os
  
  def list_directory_contents(path):
      if not os.path.exists(path):
          return []
      return os.listdir(path)