code: def filter_product_filename_generator(obs_info,nn):
      
      proposal_id = obs_info[0]
      visit_id = obs_info[1]
      instrument = obs_info[2]
      detector = obs_info[3]
      filter = obs_info[4]
  
      product_filename_dict = {}
      product_filename_dict["image"] = "hst_{}_{}_{}_{}_{}.fits".format(proposal_id,visit_id,instrument,detector,filter)
      product_filename_dict["source catalog"] = product_filename_dict["image"].replace(".fits",".cat")
  
      return(product_filename_dict)
docs: Generate image and sourcelist filenames for filter products
  
      Parameters
      ----------
      obs_info : list
          list of items that will be used to generate the filenames: proposal_id,
          visit_id, instrument, detector, and filter
      nn : string
          the single-exposure image number (NOTE: only used in
          single_exposure_product_filename_generator())
  
      Returns
      --------
      product_filename_dict : dictionary
          A dictionary containing the generated filenames.