code: def in_casapy (helper, caltable=None, selectcals={}, plotoptions={},
                 xaxis=None, yaxis=None, figfile=None):
      
      if caltable is None:
          raise ValueError ('caltable')
  
      show_gui = (figfile is None)
      cp = helper.casans.cp
  
      helper.casans.tp.setgui (show_gui)
      cp.open (caltable)
      cp.selectcal (**selectcals)
      cp.plotoptions (**plotoptions)
      cp.plot (xaxis, yaxis)
  
      if show_gui:
          import pylab as pl
          pl.show ()
      else:
          cp.savefig (figfile)
docs: This function is run inside the weirdo casapy IPython environment! A
      strange set of modules is available, and the
      `pwkit.environments.casa.scripting` system sets up a very particular
      environment to allow encapsulated scripting.