Almost, but not quite.  I wasn't able to find a clear way to leverage `heapq.merge`, hence why I adapted the code myself.  I bet there's a way to do it, but make sure any solution passes the following tests (the PR passes):

```python
    assert list(merge_sorted([2, 1, 3], [1, 2, 3], key=lambda x: x/3)) == [2, 1, 1, 2, 3, 3]
    assert list(merge_sorted([2, 3], [1, 3], key=lambda x: x/3)) == [2, 1, 3, 3]
````