Nesting Module doesn't seem to be supported at the moment

[Traveller23]

What is nesting module: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_nesting/Using_CSS_nesting
Specification: https://www.w3.org/TR/css-nesting-1/

.outer1 .outer1-1 {
    .inner1 .inner1-1 {
        width: 1em;
    }

    .inner2 .inner2-1 {
        width: 1em;
    }
}

When I try to parse the above CSS with the following code, an error is returned:

rules = tinycss2.parse_stylesheet(css)
tinycss2.parse_declaration_list(rules[0].content)

The returned error:

The actual content of the content:

[liZe]

That would be great!

[liZe]

A pull request has been opened (#55), feedback is welcome!