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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 convert_doc_to_text(filename: str = None, blob: bytes = None, config: TextProcessingConfig = _DEFAULT_CONFIG) -> str: """ Converts Microsoft Word DOC files to text. """

    antiword = tools['antiword']
    if antiword:
        if filename:
            return get_cmd_output(antiword, '-w', str(config.width), filename)
        else:
            return get_cmd_output_from_stdin(blob, antiword, '-w',
                                             str(config.width), '-')
    else:
        raise AssertionError("No DOC-reading tool available")