The examples should be doctest style I think, like:
```
Set items 0 and 1 to their negative values:

>>> a = np.array([1, 2, 3, 4])
>>> np.negative.at(a, [0, 1])
array([-1, -2,  3,  4])

Increment items 0, and 1 once and item 2 twice:

>>> a = np.array([1, 2, 3, 4])
>>> np.add.at(a, [0, 1, 2, 2], 1)
array([2, 3, 5, 4])
```
etc.