code: def _set_meta(self, title, published, category='', tags=''):
          
          slug_published = slugify(arrow.get(published).format(
              'YYYY-MM-DD HH:mm'))
          slug_title = slugify(title)
  
          header = '\n\t\t<meta name="date" content="{}" />\n'.format(published)
          if tags:
              header += '\t\t<meta name="tags" content="{}" />\n'.format(tags)
          if category:
              header += '\t\t<meta name="category" content="{}" />\n'.format(
                  category)
          if self.AUTHOR:
              header += '\t\t<meta name="authors" content="{}" />\n'.format(
                  self.AUTHOR)
          header += '\t\t<meta name="slug" content="{}"/>\n'.format(
              slug_published + '-' + slug_title)
          header += '\t</head>'
  
          return header
docs: the header
  
              :param title: the title of the post
              :param published: the date when the data
              has been published by the provider
              :param category: category of this data
              :param tags: the tags
              :type title: string
              :type published: string
              :param category: string
              :param tags: string
              :return: the complet head
              :rtype: string