code: def artifact_mime_type(instance):
      
      for key, obj in instance['objects'].items():
          if ('type' in obj and obj['type'] == 'artifact' and 'mime_type' in obj):
              if enums.media_types():
                  if obj['mime_type'] not in enums.media_types():
                      yield JSONError("The 'mime_type' property of object '%s' "
                                      "('%s') must be an IANA registered MIME "
                                      "Type of the form 'type/subtype'."
                                      % (key, obj['mime_type']), instance['id'])
  
              else:
                  info("Can't reach IANA website; using regex for mime types.")
                  mime_re = re.compile(r'^(application|audio|font|image|message|model'
                                       '|multipart|text|video)/[a-zA-Z0-9.+_-]+')
                  if not mime_re.match(obj['mime_type']):
                      yield JSONError("The 'mime_type' property of object '%s' "
                                      "('%s') should be an IANA MIME Type of the"
                                      " form 'type/subtype'."
                                      % (key, obj['mime_type']), instance['id'])
docs: Ensure the 'mime_type' property of artifact objects comes from the
      Template column in the IANA media type registry.