Social media posts are part of a collection

webapp_post.py

@@ -2149,6 +2149,7 @@ def individual_post_as_html(signing_priv_key_pem: str,
             if post_is_sensitive and reaction_str:
                 reaction_str = '<br>' + reaction_str
         post_html = '    <div ' + \
+            'itemprop="hasPart" ' + \
             'itemscope itemtype="http://schema.org/SocialMediaPosting" ' + \
             'id="' + timeline_post_bookmark + \
             '" class="' + container_class + '">\n'

webapp_timeline.py

@@ -787,7 +787,9 @@ def html_timeline(css_cache: {}, default_timeline: str,
                                     calendar_image, follow_approvals,
                                     icons_as_buttons, access_keys)
 
-    tl_str += '  <div id="timelineposts" class="timeline-posts">\n'
+    tl_str += \
+        '  <div id="timelineposts" class="timeline-posts" ' + \
+        'itemscope itemtype="http://schema.org/Collection">\n'
 
     # second row of buttons for moderator actions
     tl_str += \