Some small mistakes :

* « an object always compares equal to itself (i.e., ``x is y`` implies
``x == y``; this is true even for *NaN*) ». Actually NaN is not equal to
itself:

True
>>> f == f
False

* « The traceback printed when an unhandled exception occurs walks the
chain of :attr:`__cause__` and :attr:`__context__` attributes and prints
a separate traceback for each component of the chain, with the primary
exception at the top. » If by "primary exception" you mean the latest
one, then it's printed at the bottom, not the top.