input: Write a python function to print an ASCII art face.
  assert print_ascii_face() == "  ( _ _ )\n  | o o |\n  |  ^  |\n  | \\_/ |\n"
output: def print_ascii_face():
      return "  ( _ _ )\n  | o o |\n  |  ^  |\n  | \\_/ |\n"