docs: function removeEmptyContainers() {
    var elementWasRemoved = true;
    do {
      elementWasRemoved = false;
      _($('defs, metadata, g')).each(function(node) {
        if(!node.children.length) {
          $(node).remove();
          elementWasRemoved = true;
        }
      });
    } while(elementWasRemoved);
  }