code: def _parse_params(self, params=None):
          
          prm = self.default_params.copy()
          if params is not None: 
              prm.update(params)
   
          # Background file is essential!
          if not prm["background"]:
              print("Background file needed!")
              sys.exit()
          
          prm["background"] =  os.path.abspath(prm["background"])
          
          prm["strand"] = ""
          if prm["single"]:
              prm["strand"] = " -strand + "
          
          return prm
docs: Parse parameters.
  
          Combine default and user-defined parameters.