code: def left_click_callback_mosaic(obj, ev):
      """Get the value of the clicked voxel and show it in the panel."""
      event_pos = show_m_mosaic.iren.GetEventPosition()
  
      obj.picker.Pick(event_pos[0], event_pos[1], 0, scene)
  
      i, j, k = obj.picker.GetPointIJK()
      result_position.message = "({}, {}, {})".format(
          str(i), str(j), str(k)
      )
      result_value.message = "%.8f" % data[i, j, k]
  
imports: import os
  from dipy.data import fetch_bundles_2_subjects
  from dipy.io.image import load_nifti, load_nifti_data
  from dipy.viz import window, actor, ui
label_desc: Use image node_id 2 for calling a global function with example usage: left_click_callback_mosaic(obj, ev) without return types