pub fn get_all_windows(&self) -> Result<Vec<xlib::Window>, String> {
        let mut all = Vec::new();
        for root in self.get_roots() {
            match self.get_windows_for_root(root) {
                Ok(some_windows) => {
                    for w in some_windows {
                        all.push(*w);
                    }
                }
                Err(err) => return Err(err),
            }
        }
        Ok(all)
    }
Returns the child windows of all roots.
# Errors

Will error if root has no windows or there is an error
obtaining the root windows. See `get_windows_for_root`.
display-servers/xlib-display-server/src/xwrap/getters.rs