code: def plot_risk_exposures(exposures, ax=None,
                          title='Daily risk factor exposures'):
      
      if ax is None:
          ax = plt.gca()
  
      for col in exposures:
          ax.plot(exposures[col])
  
      configure_legend(ax, change_colors=True)
      ax.set_ylabel('Factor exposures')
      ax.set_title(title)
  
      return ax
docs: Parameters
      ----------
      exposures : pd.DataFrame
          df indexed by datetime, with factors as columns
          - Example:
                          momentum  reversal
              dt
              2017-01-01 -0.238655  0.077123
              2017-01-02  0.821872  1.520515
  
      ax :  matplotlib.axes.Axes
          axes on which plots are made. if None, current axes will be used
  
      Returns
      -------
      ax :  matplotlib.axes.Axes