code: function(attrs, value, opt) {
  
          var currentAttrs = this.get('attrs');
          var delim = '/';
          
          if (_.isString(attrs)) {
              // Get/set an attribute by a special path syntax that delimits
              // nested objects by the colon character.
  
              if (value) {
  
                  var attr = {};
                  joint.util.setByPath(attr, attrs, value, delim);
                  return this.set('attrs', _.merge({}, currentAttrs, attr), opt);
                  
              } else {
                  
                  return joint.util.getByPath(currentAttrs, attrs, delim);
              }
          }
          
          return this.set('attrs', _.merge({}, currentAttrs, attrs), value);
      }
docs: A convenient way to set nested attributes.