I have the following dataframe:

```
+--------------------+---+---+-----+----+--------+----+
|                  ak| 1 | 2 |  3  | 4  |   5    |  6 |
+--------------------+---+---+-----+----+--------+----+
|8dce120638dbdf438   |  2|  1|    0|   0|       0|   0|
|3fd28484316249e95   |  1|  0|    3|   1|       4|   5|
|3636b43f64db33889   |  9|  3|    3|   4|      18|  11|
+--------------------+---+---+-----+----+--------+----+

```

and I want transpose it to the following:

```
ak                 depth    user_count
8dce120638dbdf438    1       2
8dce120638dbdf438    2       1
8dce120638dbdf438    3       0
8dce120638dbdf438    4       0
8dce120638dbdf438    5       0
8dce120638dbdf438    6       0
3fd28484316249e95    1       1
3fd28484316249e95    2       0
3fd28484316249e95    3       3
3fd28484316249e95    4       1
3fd28484316249e95    5       4
3fd28484316249e95    6       5
3fd28484316249e95    1       9
3fd28484316249e95    2       3
3fd28484316249e95    3       3
3fd28484316249e95    4       4
3fd28484316249e95    5       18
3fd28484316249e95    6       11

```

How to do it in Scala?