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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 _set_default_attr(self, default_attr):
 """Sets default attributes when None. Args: default_attr: dict. Key-val of attr, default-value. """

        for attr, val in six.iteritems(default_attr):
            if getattr(self, attr, None) is None:
                setattr(self, attr, val)