def METHOD_NAME(self):
    data = b"H" * 123 + b"_" * 4096 + b"X" * 4096 + b"_" * 4096
    chunker = ChunkerFixed(4096, 123)
    fmap = [(0, 123, True), (123, 4096, False), (123 + 4096, 4096, True), (123 + 8192, 4096, False)]
    parts = cf(chunker.chunkify(BytesIO(data), fmap=fmap))
    # because we marked the '_' ranges as holes, we will get hole ranges instead!
    self.assert_equal(parts, [data[0:123], 4096, data[123 + 4096 : 123 + 8192], 4096])