Liquid syntax error (line 4): Expected end_of_string but found pipe in "site.tags[page.tags] | size > 0" in tags/Fedora.md

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I got warning when building jeklly that said

Liquid syntax error (line 4): Expected end_of_string but found pipe in “site.tags[page.tags] | size > 0” in tags/Fedora.md

My tags/Fedora.md are below :

---
layout: default
title: Fedora
tags: Fedora
---
<div id="home">
  <h2><i class="fa fa-tags"></i> Posts related to tag: {{ page.tags }}</h2>
  <ul id="blog-posts" class="posts">
    {% unless site.tags[page.tags] | size > 0 %}
        <p>No posts in this tag at this time.</p>
    {% endunless %}

    {% for post in site.tags[page.tags] %}
       {% assign currentDate = post.date | date: "%Y" %}
       {% if currentDate != myDate %}
           {% unless forloop.first %}{% endunless %}
           <h4>{{ currentDate }}</h4>
           {% assign myDate = currentDate %}
       {% endif %}
      <li><span>{{ post.date | date_to_string }} &raquo;</span><a href="{{ post.url }}">{{ post.title }}</a></li>
      {% if forloop.last %}{% endif %}
    {% endfor %}
  </ul>
</div>

What is the best syntax to replace the size of tags ?