class_docstr: Extracts a subregion from the source image and scales it to the output size.
  
  The fill color is used to map pixels from the source rect that fall outside
  the source image.
  
  See: https://pillow.readthedocs.io/en/latest/PIL.html#PIL.ImageTransform.ExtentTransform
code: def apply_coords(self, coords):
      # Transform image center from source coordinates into output coordinates
      # and then map the new origin to the corner of the output image.
      h, w = self.output_size
      x0, y0, x1, y1 = self.src_rect
      new_coords = coords.astype(np.float32)
      new_coords[:, 0] -= 0.5 * (x0 + x1)
      new_coords[:, 1] -= 0.5 * (y0 + y1)
      new_coords[:, 0] *= w / (x1 - x0)
      new_coords[:, 1] *= h / (y1 - y0)
      new_coords[:, 0] += 0.5 * w
      new_coords[:, 1] += 0.5 * h
      return new_coords
  
imports: import numpy
  import torch
  import torch.nn.functional
  from fvcore.transforms.transform import CropTransform, HFlipTransform, NoOpTransform, Transform, TransformList
  from PIL import Image
label_desc: Use image node_id 3 for calling the ExtentTransform obj's underlying member method code with example usage: obj.apply_coords(coords) and returns: new_coords