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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_image_dimensions(self, thumbnail):
 """ Set image dimensions from the cached dimensions of a ``Thumbnail`` model instance. """

        try:
            dimensions = getattr(thumbnail, 'dimensions', None)
        except models.ThumbnailDimensions.DoesNotExist:
            dimensions = None
        if not dimensions:
            return False
        self._dimensions_cache = dimensions.size
        return self._dimensions_cache