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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 Row(self):
 """ The class for a row in this list. """

        if not hasattr(self, '_row_class'):
            attrs = {'fields': self.fields, 'list': self, 'opener': self.opener}
            for field in self.fields.values():
                attrs[field.name] = field.descriptor
            self._row_class = type('SharePointListRow', (SharePointListRow,), attrs)
        return self._row_class