text: Title: how to use imgaug with pytorch
  Body: I want to use imgaug with pytorch. 
  def __getitem__(self, index) in torch.utils.data.Dataset can process one picture at a time, but in seq(images = images, keypoints = keypoints), I must give 4 dims (B, H, W, Channel). I want to know how to use imgaug without expansion dimension.
  Thank you!