Some liquid tags are missing on the Documentation of Red Hat 3scale API Management

Issue

We are trying the following:

{% if urls.account.active? %}
    <a class="active" href="{{ urls.account }}">Account</a>
{% else %}
    <a href="{{ urls.account }}">Account</a>
{% endif %}

But the urls.account doesn't seem to exist.

However, we did notice that the following:

{% if urls.applications.active? %}
    <a class="active" href="{{ urls.applications }}">Applications</a>
{% else %}
    <a href="{{ urls.applications }}">Applications</a>
{% endif %}

Does work. Neither ones are described in the liquid reference.

Where can we find extended documentation about the liquid references we can use?