docs: def in_casapy (helper, asdm=None, ms=None, tbuff=None):
      """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.
  
      """
      if asdm is None:
          raise ValueError ('asdm')
      if ms is None:
          raise ValueError ('ms')
      if tbuff is None:
          raise ValueError ('tbuff')
  
      helper.casans.importevla (asdm=asdm, vis=ms, ocorr_mode='co', online=True,
                                tbuff=tbuff, flagpol=False, tolerance=1.3,
                                applyflags=True, flagbackup=False)