docs: def auto_labels(df):
      """Transforms atomic system information into well-formatted labels.
  
      Parameters
      ----------
      df : Pandas DataFrame.
  
      Returns
      -------
      labels : list of system labels.
      """
      systems = list(df.system)
      facets = list(df.facet)
      systems_labels = [w.replace('_', '\ ') for w in systems]
      systems_labels = [sub(w) for w in systems_labels]
      systems_labels = [w.replace('}$$_{', '') for w in systems_labels]
      systems_labels = [w.replace('$', '') for w in systems_labels]
      systems_labels = ['$' + w + '$' for w in systems_labels]
  
      facets_label = [w.replace('_', '\ ') for w in facets]
      facets_label = ['(' + w + ')' for w in facets_label]
  
      labels = []
      for i, sys in enumerate(systems_labels):
          labels.append(sys + facets_label[i])
      # labels = list(set(labels))
      return(labels)