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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 css_one(self, path, default=NULL):
 """ Get first element which matches the given css path or raise DataNotFound. """


        try:
            return self.css_list(path)[0]
        except IndexError:
            if default is NULL:
                raise DataNotFound('CSS path not found: %s' % path)
            else:
                return default