new_contents: # -*- coding: utf-8 -*-
  from __future__ import absolute_import, division, print_function
  
  import six
  
  from polyaxon_client.exceptions import PolyaxonException
  from polyaxon_client.schemas.utils import to_list
  
  
  def validate_tags(tags):
      if not tags:
          return None
  
      if isinstance(tags, six.string_types):
          tags = [tag.strip() for tag in tags.split(',')]
      
      for tag in to_list(tags):
          if not (tag and isinstance(tag, six.string_types)):
              raise PolyaxonException(
                  'Received an invalid tag {}. '
                  'Please make sure that the tags are list of strings, '
                  'or a string containing comma separated values.'.format(tag))
      return set(tags)
  
subject: Add tags validation