new_contents: class FilterModule(object):
      ''' If input is string, just return the string; if array, merge elements '''
  
      def filters(self):
          return {
              'smart_join': self.smart_join,
          }
  
      def smart_join(self,input_value):
          if type(input_value) is str:
              return input_value
          elif type(input_value) is list:
              return "\n".join(input_value)
          else:
              raise
  
subject: add 'smart_join' filter