var StyledElement.src: String by CssProperty()

// copy pasted in my file to be accessible
private class CssProperty<T>(private val default: (() -> T)? = null) {
    operator fun getValue(thisRef: StyledElement, property: KProperty<*>): T {
        default?.let { default ->
            if (!thisRef.declarations.containsKey(property.name)) {
                thisRef.declarations[property.name] = default() as Any
            }
        }

        @Suppress("UNCHECKED_CAST")
        return thisRef.declarations[property.name] as T
    }

    operator fun setValue(thisRef: StyledElement, property: KProperty<*>, value: T) {
        thisRef.declarations[property.name] = value as Any
    }
}