Uncaught ReferenceError: Markdown is not defined - html

Question

I am trying to add markdown to my input text box for a flask project. I am following the Grinburg text book. In my forms.py I have :
from flask_pagedown.fields import PageDownField
from wtforms.fields.simple import HiddenField
class NewEntry(Form):
'''
A form for new entries
'''
title = TextAreaField("Title", validators=[Required()])
text = PageDownField("Text", validators=[Required()])
tags = TextAreaField("Tags", validators=[Required()])
srcLibEntries = HiddenField(label=None, id="srcLibArticles")
submit = SubmitField('Submit', id="new_entry_submit_button")
Over in my HTML, I have :
{% extends "layout.html" %}
{% import "bootstrap/wtf.html" as wtf %}
{% block scripts %}
{{super()}}
{{pagedown.include_pagedown()}}
{% endblock %}
{% block body %}
<form method="post" role="form">
{{ wtf.form_field(form.title) }}
{{ wtf.form_field(form.text) }}
{{ wtf.form_field(form.tags) }}
{{ form.srcLibEntries }}
{{ wtf.form_field(form.submit) }}
</form>
All this unfurls at the browser to have the following code for the text input box :
<div class="form-group required"><label class="control-label" for="text">Text</label>
<div class="flask-pagedown"><textarea class="form-control flask-pagedown-input" id="flask-pagedown-text" name="text" required>fsdafds</textarea></div>
<div class="flask-pagedown-preview" id="flask-pagedown-text-preview"></div>
<script type="text/javascript">
f = function() {
if (typeof flask_pagedown_converter === "undefined")
flask_pagedown_converter = Markdown.getSanitizingConverter().makeHtml;
var textarea = document.getElementById("flask-pagedown-text");
var preview = document.getElementById("flask-pagedown-text-preview");
textarea.onkeyup = function() { preview.innerHTML = flask_pagedown_converter(textarea.value); }
textarea.onkeyup.call(textarea);
}
if (document.readyState === 'complete')
f();
else if (window.addEventListener)
window.addEventListener("load", f, false);
else if (window.attachEvent)
window.attachEvent("onload", f);
else
f();
</script>
</div>
I am getting an exception at the browser, namely, "Uncaught ReferenceError: Markdown is not defined" and it is referring to this line :
flask_pagedown_converter = Markdown.getSanitizingConverter().makeHtml;
I don't think I have to import any more markdown anywhere. What is going on here?
Edit 1:
I needed to add the following to my layout.css:
<script src="//cdnjs.cloudflare.com/ajax/libs/pagedown/1.0/Markdown.Converter.js"> </script>
<script src="//cdnjs.cloudflare.com/ajax/libs/pagedown/1.0/Markdown.Editor.js"> </script>
<script src="//cdnjs.cloudflare.com/ajax/libs/pagedown/1.0/Markdown.Sanitizer.js"> </script>

Answer 1

I needed to add the following to my layout.css:
<script src="//cdnjs.cloudflare.com/ajax/libs/pagedown/1.0/Markdown.Converter.js"> </script>
<script src="//cdnjs.cloudflare.com/ajax/libs/pagedown/1.0/Markdown.Editor.js"> </script>
<script src="//cdnjs.cloudflare.com/ajax/libs/pagedown/1.0/Markdown.Sanitizer.js"> </script>