Django TemplateSyntaxError: Error during template rendering

问题

I am working on a Python/ Django project, having not really used either much before. I am currently getting a TemplateSyntaxError when clicking a link on one of the pages on my website.

The URL that this link takes you to (the URL for the broken page) is: costing/id/payment-report/overview & the exception value says:

Invalid block tag on line 87: 'date_to_display', expected 'elif', 'else' or 'endif'. Did you forget to register or load this tag?

The template (HTML file) itself for this page, doesn't actually have this variable anywhere in it. The location of the template in the folder structure is: costing/templates/costing/reports_post_deposit.html, however, there is another template file at costing/pdf2_base.html, which does contain this variable within the structure:

<body>
    ...
    {% block content_payment_schedule %}
        {% if not webview %}
            <div>
                <table>
                    ...
                    <tr>
                        ...
                        <td> {% date_to_display %} </td>
                    </tr>
                </table>
            </div>
        {% endif %}
        ...
    {% endblock %}
    ...

</body>

So I can see that the variable it's complaining about is used within this template. The page at costing/id/payment-report/overview is used to generate a PDF file from information stored in the database, and information provided by the user. The structure of this PDF file is defined in the costing/pdf2_base.html file- and date_to_display is a a variable whose value I wanted to add to the PDF generated...

What do I need to do to register or load this tag, as the error message says I need to do?