knnMatch with trainDescriptors is missing about evision HOT 1 CLOSED

defmodule DiffBench do
  def get_keypoints!(img) do
    gray = Evision.cvtColor!(img, Evision.cv_COLOR_RGB2GRAY)
    sift = Evision.AKAZE.create!()
    kp = Evision.AKAZE.detect!(sift, gray)
   Evision.AKAZE.compute!(sift, gray, kp)
  end
end

base = Evision.imread!("base_img.jpg")
target = Evision.imread!("target_img.jpg")
{_, des_base} = DiffBench.get_keypoint!(base)
{_, des_target} = DiffBench.get_keypoint!(target)

bf = Evision.BFMatcher.bfMatcher!()
matches = Evision.BFMatcher.knnMatch!(bf, des_base, des_target, 2)