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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 unicode_is_ascii(u_string):
 """Determine if unicode string only contains ASCII characters. :param str u_string: unicode string to check. Must be unicode and not Python 2 `str`. :rtype: bool """

    assert isinstance(u_string, str)
    try:
        u_string.encode('ascii')
        return True
    except UnicodeEncodeError:
        return False