產生器物件
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Generator objects are what Python uses to implement generator
iterators. They are normally created by iterating over a function that
yields values, rather than explicitly calling "PyGen_New()".

PyGenObject

   The C structure used for generator objects.

PyTypeObject PyGen_Type

   The type object corresponding to generator objects.

int PyGen_Check(ob)

   Return true if *ob* is a generator object; *ob* must not be *NULL*.

int PyGen_CheckExact(ob)

   Return true if *ob*’s type is *PyGen_Type* is a generator object;
   *ob* must not be *NULL*.

PyObject* PyGen_New(PyFrameObject *frame)
    *Return value: New reference.*

   Create and return a new generator object based on the *frame*
   object. A reference to *frame* is stolen by this function. The
   parameter must not be *NULL*.
