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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 size(pathname):
 """ Returns size of a file or folder in Bytes :param pathname: path to file or folder to be sized :type pathname: str :return: size of file or folder in Bytes :rtype: int :raises: os.error if file is not accessible """

    if os.path.isfile(pathname):
        return os.path.getsize(pathname)
    return sum([size('{}/{}'.format(pathname, name)) for name in get_content_list(pathname)])