code: def __init__(self):
      # initialize the SIFT feature extractor for OpenCV 2.4
      if is_cv2():
          self.extractor = cv2.DescriptorExtractor_create("SIFT")
  
      # otherwise initialize the SIFT feature extractor for OpenCV 3+
      else:
          self.extractor = cv2.xfeatures2d.SIFT_create()
  
imports: from __future__ import absolute_import
  import numpy
  import cv2
  from ..convenience import is_cv2
label_desc: Use image node_id 1 to create a new RootSIFT object  with example: obj = RootSIFT()