Iterator Protocol
*****************

There are two functions specifically for working with iterators.

int PyIter_Check(PyObject *o)
    * Part of the Stable ABI since version 3.8.*

   Return non-zero if the object *o* can be safely passed to
   "PyIter_NextItem()" and "0" otherwise. This function always
   succeeds.

int PyAIter_Check(PyObject *o)
    * Part of the Stable ABI since version 3.10.*

   Return non-zero if the object *o* provides the "AsyncIterator"
   protocol, and "0" otherwise.  This function always succeeds.

   Added in version 3.10.

int PyIter_NextItem(PyObject *iter, PyObject **item)
    * Part of the Stable ABI since version 3.14.*

   Return "1" and set *item* to a *strong reference* of the next value
   of the iterator *iter* on success. Return "0" and set *item* to
   "NULL" if there are no remaining values. Return "-1", set *item* to
   "NULL" and set an exception on error.

   Added in version 3.14.

PyObject *PyIter_Next(PyObject *o)
    *Return value: New reference.** Part of the Stable ABI.*

   This is an older version of "PyIter_NextItem()", which is retained
   for backwards compatibility. Prefer "PyIter_NextItem()".

   Return the next value from the iterator *o*.  The object must be an
   iterator according to "PyIter_Check()" (it is up to the caller to
   check this). If there are no remaining values, returns "NULL" with
   no exception set. If an error occurs while retrieving the item,
   returns "NULL" and passes along the exception.

type PySendResult

   The enum value used to represent different results of
   "PyIter_Send()".

   Added in version 3.10.

PySendResult PyIter_Send(PyObject *iter, PyObject *arg, PyObject **presult)
    * Part of the Stable ABI since version 3.10.*

   Sends the *arg* value into the iterator *iter*. Returns:

   * "PYGEN_RETURN" if iterator returns. Return value is returned via
     *presult*.

   * "PYGEN_NEXT" if iterator yields. Yielded value is returned via
     *presult*.

   * "PYGEN_ERROR" if iterator has raised an exception. *presult* is
     set to "NULL".

   Added in version 3.10.
