code: def plot(Si_df, ax=None):
      """Create bar chart of results.
  
  
      Examples
      --------
          >>> from SALib.plotting.bar import plot as barplot
          >>> from SALib.test_functions import Ishigami
          >>>
          >>> # See README for example problem specification
          >>>
          >>> X = saltelli.sample(problem, 512)
          >>> Y = Ishigami.evaluate(X)
          >>> Si = sobol.analyze(problem, Y, print_to_console=False)
          >>> total, first, second = Si.to_df()
          >>> barplot(total)
  
  
      Parameters
      ----------
      * Si_df: pd.DataFrame, of sensitivity results
  
      Returns
      -------
      * ax : matplotlib axes object
      """
      conf_cols = Si_df.columns.str.contains(CONF_COLUMN)
  
      confs = Si_df.loc[:, conf_cols]
      confs.columns = [
          c.replace(CONF_COLUMN, "") for c in confs.columns
      ]
  
      Sis = Si_df.loc[:, ~conf_cols]
  
      ax = Sis.plot(kind="bar", yerr=confs, ax=ax)
      return ax
  
label_desc: Use image node_id 1 for calling a global function with example usage: plot(Si_df, ax) and returns: ax