Add to installed apps

'crispy_forms',
'ajax_helpers',
'django_modals',
'show_src_code',

Add to template

{% load static src_code %}
{% highlightjs_includes %}
<script src="{% static 'ajax_helpers/ajax_helpers.js' %}"></script>
<link href="{% static 'ajax_helpers/ajax_helpers.css' %}" rel="stylesheet"/>    
<script src="{% static 'django_modals/js/modals.js' %}"></script>
<link rel="stylesheet" type="text/css" href="{% static 'django_modals/css/modals.css' %}"/>

Create subclass of BaseSourceCodeModal

from show_src_code.modals import BaseSourceCodeModal

class SourceCodeModal(BaseSourceCodeModal):
    code = {
        'code_identifier', Function or Class to display
    }

Add to urls

path('source_code/<str:slug>', views.SourceCodeModal.as_view(), name='source_code')

In template

{% load src_code%}   
{% show_src_code 'source_code' 'code:id' %}