code: def count_visible(ul, br, joints_3d):
      """Count number of visible joints given bound ul, br"""
      vis = np.logical_and.reduce(
          (
              joints_3d[:, 0, 0] > 0,
              joints_3d[:, 0, 0] > ul[0],
              joints_3d[:, 0, 0] < br[0],
              joints_3d[:, 1, 0] > 0,
              joints_3d[:, 1, 0] > ul[1],
              joints_3d[:, 1, 0] < br[1],
              joints_3d[:, 0, 1] > 0,
              joints_3d[:, 1, 1] > 0,
          )
      )
      return np.sum(vis), vis
  
imports: from __future__ import absolute_import
  from __future__ import division
  import math
  import random
  import numpy
  import mxnet
  from mxnet import nd, image
  from mxnet.gluon.data.vision import transforms
  from ...utils.filesystem import try_import_cv2
label_desc: Use image node_id 19 for calling a global function with example usage: count_visible(ul, br, joints_3d) and returns: np,  vis