Creation of GC'd types is explained at
<http://docs.python.org/c-api/gcsupport.html>.

The docs claim that PyObject_GC_Track must be called once an object
created with PyObject_GC_New is initialized.  The docs fail to explain
what should be done if there is an error during initialization of an
object created with PyObject_GC_New.  Should PyObject_GC_Track still be
called?  Should some other API be called to free the object?

Overall, the docs are missing an explanation of the overall working of
the GC and GC APIs, so it is hard to build an understanding of the
system.  Without an understand, it's difficult to read between the lines
of the API docs, meaning they need to cover every possible case, which
they don't currently.