code: def html_content(self):
          
          context = self.acquire_context()
          try:
              return render_placeholder(self.content_placeholder, context)
          except (AttributeError, KeyError):
              # Should happen when ``context`` and ``request``
              # have not been found in the stack.
              pass
          return self.content
docs: Render the content_placeholder field dynamicly.
          https://github.com/Fantomas42/cmsplugin-zinnia/issues/3