HTMLNode

Next, we need a way to represent HTML nodes.

Our "TextNode" class represents the various types of inline text that can exist in HTML and Markdown.
Our "HTMLNode" class will represent a "node" in an HTML document tree (like a <p> tag and its contents, or an <a> tag and its contents). It can be block level or inline, and is designed to only output HTML.

Assignment

Create a new file called htmlnode.py in the src directory and define a class called HTMLNode in it.
The HTMLNode class should have 4 data members set in the constructor:
- tag - A string representing the HTML tag name (e.g. "p", "a", "h1", etc.)
- value - A string representing the value of the HTML tag (e.g. the text inside a paragraph)
- children - A list of HTMLNode objects representing the children of this node
- props - A dictionary of key-value pairs representing the attributes of the HTML tag. For example, a link (<a> tag) might have {"href": "https://www.google.com"}
Perhaps counterintuitively, every data member should be optional and default to None:
- An HTMLNode without a tag will just render as raw text
- An HTMLNode without a value will be assumed to have children
- An HTMLNode without children will be assumed to have a value
- An HTMLNode without props simply won't have any attributes
Add a to_html(self) method. For now, it should just raise a NotImplementedError. Child classes will override this method to render themselves as HTML.
Add a props_to_html(self) method. It should return a formatted string representing the HTML attributes of the node. For example, if self.props is:

{
    "href": "https://www.google.com",
    "target": "_blank",
}

Then self.props_to_html() should return:

 href="https://www.google.com" target="_blank"

Notice the leading space character before href and before target. This is important. HTML attributes are always separated by spaces. If self.props is None or empty, return an empty string.

Add a __repr__(self) method. Give yourself a way to print an HTMLNode object and see its tag, value, children, and props. This will be useful for your debugging.
Create some tests for the HTMLNode class (at least 3). I used a new file called src/test_htmlnode.py. Create a few nodes and make sure the props_to_html method works as expected.

Run and submit the CLI tests.