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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 vector_mask(self):
 """ Returns vector mask associated with this layer. :return: :py:class:`~psd_tools.api.shape.VectorMask` or `None` """

        if not hasattr(self, '_vector_mask'):
            self._vector_mask = None
            blocks = self.tagged_blocks
            for key in ('VECTOR_MASK_SETTING1', 'VECTOR_MASK_SETTING2'):
                if key in blocks:
                    self._vector_mask = VectorMask(blocks.get_data(key))
        return self._vector_mask