code: def side(sankey, n=1):
      """Generate a side chain."""
      prior = len(sankey.diagrams)
      for i in range(0, 2 * n, 2):
          sankey.add(
              flows=[1, -1],
              orientations=[-1, -1],
              patchlabel=str(prior + i),
              prior=prior + i - 1,
              connect=(1, 0),
              alpha=0.5,
          )
          sankey.add(
              flows=[1, -1],
              orientations=[1, 1],
              patchlabel=str(prior + i + 1),
              prior=prior + i,
              connect=(1, 0),
              alpha=0.5,
          )
  
imports: import matplotlib.pyplot
  from matplotlib.sankey import Sankey
label_desc: Use image node_id 1 for calling a global function with example usage: side(sankey, n) without return types