docs: def compress_multiple_pdfs(source_directory, output_directory, ghostscript_binary):
      """Compress all PDF files in the current directory and place the output in the
      given output directory. This is a generator function that first yields the amount
      of files to be compressed, and then yields the output path of each file.
  
      Args:
          source_directory (str): Filepath to the source directory.
          output_directory (str): Filepath to the output directory.
          ghostscript_binary (str): Name of the Ghostscript binary.
  
      Returns:
          list(str): paths to outputs.
      """
      source_paths = _get_pdf_filenames_at(source_directory)
      yield len(source_paths)
      for source_path in source_paths:
          output = os.path.join(output_directory, os.path.basename(source_path))
          compress_pdf(source_path, output, ghostscript_binary)
          yield output