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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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