code: def postProcess(pool, namespace=""):
      # Add missing descriptors which are not computed yet, but will be for the
      # final release or during the 1.x cycle. However, the schema need to be
      # complete before that, so just put default values for these.
      # Also make sure that some descriptors that might have fucked up come out nice.
  
      rhythmspace = "rhythm."
      if namespace:
          rhythmspace = namespace + ".rhythm."
  
      pool.set(rhythmspace + "bpm_confidence", 0.0)
      pool.set(rhythmspace + "perceptual_tempo", "unknown")
  
      descriptors = pool.descriptorNames()
      if not pool.containsKey(rhythmspace + "beats_loudness"):
          pool.set(rhythmspace + "beats_loudness", 0.0)
          pool.set(rhythmspace + "beats_loudness_bass", 0.0)
  
      # PCA analysis of spectral contrast output:
      pca(pool, namespace)
  
imports: import essentia
  import essentia.standard
  import essentia.streaming
  from essentia import Pool
  from numpy import mean, var
label_desc: Use image node_id 2 for calling a global function with example usage: postProcess(pool, namespace) without return types