docs: def plot_histograms_it_extra_dims(dataobj, keys, extra_dims, **kwargs):
      """Produce histograms for each group of extra dimensions. \*\*kwargs are
      directly passed on to plot_histograms().
  
  
      """
      if isinstance(dataobj, pd.DataFrame):
          df = dataobj
      else:
          df = dataobj.df
  
      g = df.groupby(extra_dims)
  
      results = {}
      for name in sorted(g.groups.keys()):
          item = g.get_group(name)
          plot_results = plot_histograms(item, keys, **kwargs)
          results[name] = plot_results
  
      return results