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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 ensure_unicode(str_or_unicode):
 """ tests, if the input is ``str`` or ``unicode``. if it is ``str``, it will be decoded from ``UTF-8`` to unicode. """

    if isinstance(str_or_unicode, str):
        return str_or_unicode.decode('utf-8')
    elif isinstance(str_or_unicode, unicode):
        return str_or_unicode
    else:
        raise ValueError("Input '{0}' should be a string or unicode, "
                         "but its of type {1}".format(str_or_unicode,
                                                      type(str_or_unicode)))