Dataset before extension:
 [ 0 -1 -2 -3 -4 -5 -6 ]
 [ 0 0 0 0 0 0 0 ]
 [ 0 1 2 3 4 5 6 ]
 [ 0 2 4 6 8 10 12 ]

Filter type is: H5Z_FILTER_DEFLATE

Dataset after extension:
 [ 0 -1 -2 -3 -4 -5 -6 7 8 9 ]
 [ 0 0 0 0 0 0 0 7 8 9 ]
 [ 0 1 2 3 4 5 6 7 8 9 ]
 [ 0 2 4 6 8 10 12 7 8 9 ]
 [ 0 1 2 3 4 5 6 7 8 9 ]
 [ 0 1 2 3 4 5 6 7 8 9 ]

