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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 ruencode(string, extension=False):
 """Encode a string using 'rotunicode' codec. :param string: The input string to encode. :type string: `basestring` :param extension: True if the entire input string should be encoded. False to split the input string using :func:`os.path.splitext` and encode only the file name portion keeping the extension as is. :type extension: `bool` :return: Encoded string. :rtype: `unicode` """

    if extension:
        file_name = string
        file_ext = ''
    else:
        file_name, file_ext = splitext(string)

    encoded_value, _ = _ROT_UNICODE.encode(file_name)
    return encoded_value + file_ext