Parsing this markdown block:

```python # Line 1 # Line 2 ```  {: .no_line_numbers}

(space after ``` only to allow github markdown parsing)

with fenced_code and attr_list extensions enabled with default settings

renders this html:

<pre><code class="python"># Line 1 # Line 2 </code></pre> <p>{:&nbsp;.no_line_numbers}</p>

There doesn't seem to be a way to manually specify attributes for code blocks in the current implementation.