code: def do_import(self, name, default):
          
          try:
              option = getattr(self.options, name)
              if option:
                  klass = import_class(option)
              else:
                  klass = default
              setattr(self.options, name, klass)
          except Exception as e:
              self.parser.error('Unable to import "%s": %s' % (name, e))
docs: Import the given option (use default values if not defined on command line)