code: def _handle_four_channel_image(img, alpha):
      if alpha is None:
          raise ValueError(
              "An RGBA image is read by chainercv.utils.read_image, "
              "but the `alpha` option is not set. Please set the option so that "
              "the function knows how to handle RGBA images."
          )
      elif alpha == "ignore":
          img = img[:, :, :3]
      elif alpha == "blend_with_white":
          color_channel = img[:, :, :3]
          alpha_channel = img[:, :, 3:] / 255
          img = color_channel * alpha_channel + 255 * np.ones_like(
              color_channel
          ) * (1 - alpha_channel)
      elif alpha == "blend_with_black":
          color_channel = img[:, :, :3]
          alpha_channel = img[:, :, 3:] / 255
          img = color_channel * alpha_channel
      return img
  
file_path: chainercv/chainercv/utils/image/read_image.py
imports: from __future__ import division
  import chainer
  import numpy
  from PIL import Image
label_desc: Use image node_id 1 for calling a global function with example usage: _handle_four_channel_image(img, alpha) and returns: img