code: def update_lines(num, walks, lines):
      for line, walk in zip(lines, walks):
          # NOTE: there is no .set_data() for 3 dim data...
          line.set_data(walk[:num, :2].T)
          line.set_3d_properties(walk[:num, 2])
      return lines
  
imports: import matplotlib.pyplot
  import numpy
  import matplotlib.animation
label_desc: Use image node_id 2 for calling a global function with example usage: update_lines(num, walks, lines) and returns: lines