The functions in this chapter are specific to certain Python object
types. Passing them an object of the wrong type is not a good idea;
if you receive an object from a Python program and you are not sure
that it has the right type, you must perform a type check first;
for example, to check that an object is a dictionary, use
PyDict_Check(). The chapter is structured like the
``family tree'' of Python object types.
Warning:
While the functions described in this chapter carefully check
the type of the objects which are passed in, many of them do not check
for NULL being passed instead of a valid object. Allowing NULL
to be passed in can cause memory access violations and immediate
termination of the interpreter.