input: Write a function to list the contents of a given directory using Python. The function should accept a directory path as input and return a list of all contents within that directory, including files and subdirectories.
  assert list_directory_contents('/path/to/directory/1')==['file1.txt', 'file2.txt', 'subdir1', 'subdir2']
  assert list_directory_contents('/path/to/directory/2')==['file3.txt', 'file4.txt', 'subdir3']
  assert list_directory_contents('/path/to/directory/3')==['file5.txt', 'subdir4']
  assert list_directory_contents('/nonexistent/directory')==[]
output: import os
  
  def list_directory_contents(directory_path):
      if not os.path.exists(directory_path):
          return []
      return os.listdir(directory_path)