なぜ?html?

{% extends "base.html" %} 
{% import "bootstrap/wtf.html" as wtf %} 
{% block title %}index{% endblock %} 
{% block body %} 
<div class='page-header'> 
<h1>hello,{% if name %}{{name}}{% else %}Stranger{% endif %}!h1> 
div> 
{{wtf.quick_form(form)}} 
{% endblock %} 

from flask import Flask 
from flask_bootstrap import Bootstrap 
app = Flask(__name__) 
bootstrap = Bootstrap(app)