Append child node at the last of child nodes.

        If this instance is connected to the node on browser, the child node is
        also added to it.

def appendChild(self, child: 'WdomElement') -> Node:
        """Append child node at the last of child nodes.

        If this instance is connected to the node on browser, the child node is
        also added to it.
        """
        if self.connected:
            self._append_child_web(child)
        return self._append_child(child)