About ImbalancedDataSampler

I want to know whether ImbalancedDataSampler in this link is present in pytorch are not. When I run (?torch.utils.data.Sampler), I am seeing it as one of the subclasses of torch.utils.data.Sampler. But, there is nothing mentioned about it in pytorch documentation and also in source code. I am confused. Please help. Thanks in

Init signature: torch.utils.data.Sampler(data_source)
Base class for all Samplers.

Every Sampler subclass has to provide an __iter__ method, providing a way
to iterate over indices of dataset elements, and a __len__ method that
returns the length of the returned iterators.
File:           /home/AIX_Common/__files__/opt/anaconda2/envs/ai-gpu/lib/python3.6/site-packages/torch/utils/data/sampler.py
Type:           type
Subclasses:     SequentialSampler, RandomSampler, SubsetRandomSampler, WeightedRandomSampler, BatchSampler, DistributedSampler, SortSampler, SortishSampler, ImbalancedDatasetSampler