How should I use parse_mode='HTML' in a Telegram Python bot?

I'm trying to send a message in a channel with a bot using Telegram API's send_photo() method. It takes a caption parameter (type String) but I can't format it through the parse_mode='HTML' parameter. If I use:

send_photo(chat_id, photo, caption="<b>Some text</b>", parse_mode='HTML')

it sends the message but without formatting. Why?

First, you need to import ParseMode from telegram:

from telegram import ParseMode

Then, specify parse_mode=ParseMode.HTML:

def jordan(bot, update):
    chat_id = update.message.chat.id
    with open('JordanPeterson.jpg', 'rb') as jordan_picture:
        caption = "<a href='https://twitter.com/jordanbpeterson'>Jordan B. Peterson</a>"
        bot.send_photo(
            chat_id,
            photo=jordan_picture,
            caption=caption,
            parse_mode=ParseMode.HTML
        )

It works:

Both parse_mode='html' (suggested by slackmart) and parse_mode='HTML' that you used yourself work for me! As per your comment: You can use multiple tags. Here's an example with hyperlink, bold, and italic:

Regarding your comment:

...do I have any limitations on HTML tags? I can't use something like <img> or <br> to draw a line

Try and find out. That's what I did!

Now you're trying to format the caption of an image using HTML, meaning you're formatting a text, so obviously you can't use "something like <img>." It has to be a text formatting tag (plus <a>). I believe you can only use: <a>, <b>, <strong>, <i> and <em>. If you try to use a text-formatting tag like <del>, it will give you this error:

Can't parse entities: unsupported start tag "del" at byte offset 148