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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 is_unicode(value):
 """ Check if a value is a valid unicode string, compatible with python 2 and python 3 True True False False False """

    python_version = sys.version_info[0]

    if python_version == 2:
        return isinstance(value, unicode)
    elif python_version == 3:
        return isinstance(value, str)
    else:
        raise NotImplementedError()