When is CocoKeypoints called

[liudadan]

I used the program to read the coco dataset and found that the code did not call the code of the cocoKeypoints class. But in fact, the program does call the CocoKeypoints class. When did the program call the CocoKeypoints class.
class CocoKeypoints(CocoDataset):
def __ init__ (self, cfg, dataset, heatmap_generator=None, offset_generator=None, transforms=None):
super().__ init__ (cfg, dataset)
self.num_ joints = cfg.DATASET.NUM_ JOINTS
self.num_ joints_ with_ center = self.num_ joints+1
self.sigma = cfg.DATASET.SIGMA
self.center_ sigma = cfg.DATASET.CENTER_ SIGMA
self.bg_ weight = cfg.DATASET.BG_ WEIGHT
self.heatmap_ generator = heatmap_ generator
self.offset_ generator = offset_ generator
self.transforms = transforms
self.ids = [
img_ id
for img_ id in self.ids
if len(self.coco.getAnnIds(imgIds=img_id, iscrowd=None)) > 0
]