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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_string(thing):
 """Python character arrays are a mess. If Python2, check if **thing** is an :obj:`unicode` or a :obj:`str`. If Python3, check if **thing** is a :obj:`str`. :param thing: The thing to check. :returns: ``True`` if **thing** is a string according to whichever version of Python we're running in. """

    if _util._py3k: return isinstance(thing, str)
    else: return isinstance(thing, basestring)