    def get_child(self, id_):
        """Get a child with given id in the whole child tree."""
        for child in self:
            if child.get('id') == id_:
                return child
            grandchild = child.get_child(id_)
            if grandchild:
                return grandchild
Get a child with given id in the whole child tree.
weasyprint/svg/__init__.py