title: Flash Flasks messages with a list of categories to HTML5 jinja2 template
body: <p>The idea is to use an advanced multiform, where i want to target the flash messages.</p>
  
  <p>It is possible to specify categories 'a', 'b' in flask writing a line for each category and using the category argument.</p>
  
  <p>This generates a bit of redundant code, so, would like to know if it is possible to send a list in category argument and filter it instead. </p>
  
  <p>One way of doing this is using a for in Python and for each n desired categories resend the flash n times, it would be better to simply send one flash with all desired categories.</p>
  
  <p>Using in flask the categories like so: <br/>
  <b> using python</b></p>
  
  <pre><code>@app.route('/')
  def app_session():
      flash('This is a flash message with category a', 'a')
      flash('This is a flash with category b', 'b')
      return render_template('template.html')
  </code></pre>
  
  <p><b>using HTML5 and jinja2</b></p>
  
  <pre><code>&lt;p&gt;
      {% with messages = get_flashed_messages(category_filter=["a"]) %}
          {% if messages %}
              &lt;ul class=flashes&gt;
                  {% for message in messages %}
                      &lt;li&gt;{{ message }}&lt;/li&gt;                              
                  {% endfor %}
              &lt;/ul&gt;
          {% endif %}
      {% endwith %}
  &lt;/p&gt;
  </code></pre>
  
  <p>Now an idea is to:</p>
  
  <pre><code>#in python
  flash('This is a flash message with categories a and c ', ['a','c'])
  #in both html5 jinjas
  {% with messages = get_flashed_messages(category_filter=["c"]) %}
  </code></pre>
  
  <p>Cheers</p>