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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 replace_suffix (name, new_suffix):
 """ Replaces the suffix of name by new_suffix. If no suffix exists, the new one is added. """

    assert isinstance(name, basestring)
    assert isinstance(new_suffix, basestring)
    split = os.path.splitext (name)
    return split [0] + new_suffix