Flask How to make a tree in jinja2 html?

I have in python a dictionary that represents a tree style parent child relationship. I want to display the dictionary on the webpage. FYI: The dictionary will end up being all names and will very base on the person entering info.

Example dictionary from Python:

dict_ = {'A':['B', 'C'], 'B':['D','E'], 'C':['F', 'G', 'H'], 'E':['I', 'J']}
root = 'A'

The desired HTML output display would be.

A
├── B
│   ├── D
│   └── E
│       ├── I
│       └── J
└── C
    ├── F
    ├── G
    └── H

I not sure how to get this type of display using flask, Jinja, of other options like javascript. Some guidance, partial, or full answers would be great. ( I did learn how to use treelib to display it in terminal but not html.)

Solution

In my solution, a helper function is used to create a tree consisting of dicts from the given dict with the lists it contains. Thus, the hierarchy is given to render a structure of nested list elements with a jinja macro.

def tree_find(e, t):
    if e in t:
        return t
    for v in t.values():
        r = tree_find(e, v)
        if r:
            return r
    return None

@app.route('/')
def index():
    dict_ = {'A':['B', 'C'], 'B':['D','E'], 'C':['F', 'G', 'H'], 'E':['I', 'J']}
    tree = {}
    for k,v in dict_.items():
        n = tree_find(k, tree)
        (tree if not n else n)[k] = {e:{} for e in v}
    return render_template('index.html', **locals())

{% macro render_tree(d) -%}
    <ul>
    {% for k,v in d.items(): -%}
        <li><span>{{k}}</span>
        {% if v -%}
        {{ render_tree(v) }}
        {% endif -%}
        </li>
    {% endfor -%}
    </ul>
{%- endmacro %}

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>Tree</title>
    <style type="text/css">

        ul, li {
            position: relative;
        }

        ul {
            list-style: none;
            padding-left: 16px;
        }

        li::before, li::after {
            content: "";
            position: absolute;
            left: -12px;
        }

        li::before {
            border-top: 1px solid #000;
            top: 9px;
            width: 8px;
            height: 0;
        }

        li::after {
            border-left: 1px solid #000;
            height: 100%;
            width: 0px;
            top: 2px;
        }

        ul > li:last-child::after {
            height: 8px;
        }

    </style>
</head>
<body>
    {{ render_tree(tree) }}
</body>
</html>