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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 _get_bolean_mask(self, mask):
 """Cast to two dimensional boolean mask."""

        if mask.dtype.kind == 'f':
            warnings.warn("mask image should be unsigned byte between 0"
                          " and 255. Got a float array")
        if mask.ndim == 2:
            boolean_mask = mask == 255
        elif mask.ndim == 3:
            # if all channels are white, mask out
            boolean_mask = np.all(mask[:, :, :3] == 255, axis=-1)
        else:
            raise ValueError("Got mask of invalid shape: %s" % str(mask.shape))
        return boolean_mask