Users of PySequence_GET_FAST() should get the length of the sequence using
PySequence_Size(), not PyObject_Size(): the later considers the mapping
methods as well as the sequence methods, which is not needed here. Either
should be equally fast in this case, but PySequence_Size() offers a better
conceptual match.
diff --git a/Doc/api/api.tex b/Doc/api/api.tex
index 57c1008..613f62c 100644
--- a/Doc/api/api.tex
+++ b/Doc/api/api.tex
@@ -2016,7 +2016,7 @@
Return the \var{i}th element of \var{o}, assuming that \var{o} was
returned by \cfunction{PySequence_Fast()}, and that \var{i} is within
bounds. The caller is expected to get the length of the sequence by
-calling \cfunction{PyObject_Size()} on \var{o}, since lists and tuples
+calling \cfunction{PySequence_Size()} on \var{o}, since lists and tuples
are guaranteed to always return their true length.
\end{cfuncdesc}