data[1] = [[41, 42], [11, 12]]
    data[2] = [[[51, 52], [21, 22]], [[1, 2], [31, 32]]]
    merged = [[1, 2], [11, 12], [21, 22], [31, 32], [41, 42],
              [51, 52], [61, 62]]
```

This method can be used to merge partitions created by `dynamic_partition`
as illustrated on the following example:

```python
    # Apply function (increments x_i) on elements for which a certain condition