How to add legend on html with folium?

I used this code to generate coordinates on html, but I want to add a legend to this html, what should I do?

import folium

m = folium.Map(location=[45.5236, -122.6750])
html = 'Hello'
popup=folium.Popup(html,show=True,max_width=400)
folium.Circle(
    location = [45.372, -122.6972],
    radius = 100,
    popup=popup,
    color='red',
    fill=True,
    fill_opacity=0.1
).add_to(m)
m.save(r'E:/test.html')

I want the effect like this:

Solution

As r-beginners said.

I use this example to add legend.

from branca.element import Template, MacroElement
import folium

template = """
{% macro html(this, kwargs) %}

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>jQuery UI Draggable - Default functionality</title>
  <link rel="stylesheet" href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">

  <script src="https://code.jquery.com/jquery-1.12.4.js"></script>
  <script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
  
  <script>
  $( function() {
    $( "#maplegend" ).draggable({
                    start: function (event, ui) {
                        $(this).css({
                            right: "auto",
                            top: "auto",
                            bottom: "auto"
                        });
                    }
                });
});

  </script>
</head>
<body>

 
<div id='maplegend' class='maplegend' 
    style='position: absolute; z-index:9999; border:2px solid grey; background-color:rgba(255, 255, 255, 0.8);
     border-radius:6px; padding: 10px; font-size:14px; right: 20px; bottom: 20px;'>
     
<div class='legend-title'>Legend (draggable!)</div>
<div class='legend-scale'>
  <ul class='legend-labels'>
    <li><span style='background:red;opacity:0.7;'></span>Big</li>
    <li><span style='background:orange;opacity:0.7;'></span>Medium</li>
    <li><span style='background:green;opacity:0.7;'></span>Small</li>

  </ul>
</div>
</div>
 
</body>
</html>

<style type='text/css'>
  .maplegend .legend-title {
    text-align: left;
    margin-bottom: 5px;
    font-weight: bold;
    font-size: 90%;
    }
  .maplegend .legend-scale ul {
    margin: 0;
    margin-bottom: 5px;
    padding: 0;
    float: left;
    list-style: none;
    }
  .maplegend .legend-scale ul li {
    font-size: 80%;
    list-style: none;
    margin-left: 0;
    line-height: 18px;
    margin-bottom: 2px;
    }
  .maplegend ul.legend-labels li span {
    display: block;
    float: left;
    height: 16px;
    width: 30px;
    margin-right: 5px;
    margin-left: 0;
    border: 1px solid #999;
    }
  .maplegend .legend-source {
    font-size: 80%;
    color: #777;
    clear: both;
    }
  .maplegend a {
    color: #777;
    }
</style>
{% endmacro %}"""


m = folium.Map(location=[45.5236, -122.6750])
html = 'Hello'
popup=folium.Popup(html,show=True,max_width=400)
folium.Circle(
    location = [45.372, -122.6972],
    radius = 100,
    popup=popup,
    color='red',
    fill=True,
    fill_opacity=0.1
).add_to(m)
macro = MacroElement()
macro._template = Template(template)

m.get_root().add_child(macro)
url = 'myTest.html'
m.save(url)