code: def in_casapy(helper, ms=None, plotdest=None):
      
      import numpy as np, os
  
      if ms is None:
          raise ValueError('ms')
      if plotdest is None:
          raise ValueError('plotdest')
  
      opac = helper.casans.plotweather(vis=ms, plotName=plotdest)
      opac = np.asarray(opac)
      with open(helper.temppath('opac.npy'), 'wb') as f:
          np.save(f, opac)
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.