It was listed as `binaryfunc`. It should be `unaryfunc`.
+---------------------------------------------------------+-----------------------------------+--------------+
| :c:member:`~PyNumberMethods.nb_inplace_true_divide` | :c:type:`binaryfunc` | __truediv__ |
+---------------------------------------------------------+-----------------------------------+--------------+
- | :c:member:`~PyNumberMethods.nb_index` | :c:type:`binaryfunc` | __index__ |
+ | :c:member:`~PyNumberMethods.nb_index` | :c:type:`unaryfunc` | __index__ |
+---------------------------------------------------------+-----------------------------------+--------------+
| :c:member:`~PyNumberMethods.nb_matrix_multiply` | :c:type:`binaryfunc` | __matmul__ |
| | | __rmatmul__ |