How to use the @fluentui/react.ToolbarItem.className function in @fluentui/react

(builder, keys) =>
      builder
        .click(`.${ToolbarItem.className}:nth-child(1)`)
        .snapshot('Shows menu')
        .keys(`.${ToolbarMenuItem.className}:nth-child(1)`, keys.rightArrow)
        .snapshot('Opens submenu'),
  ],

(builder, keys) =>
      builder
        .click(`.${ToolbarItem.className}:nth-child(1)`)
        .snapshot('Shows menu')
        .keys(`.${ToolbarMenuItem.className}`, keys.downArrow)
        .snapshot('Moves focus to second item in menu'),
  ],

builder =>
      builder
        .click(`.${ToolbarItem.className}:nth-child(1)`)
        .snapshot('Shows first popup')
        .click(`.${ToolbarItem.className}:nth-child(2)`)
        .snapshot('Shows second popup'),
  ],

builder =>
      builder
        .click(`.${ToolbarItem.className}:nth-child(1)`)
        .snapshot('Shows menu')
        .click(`.${ToolbarMenuItem.className}:nth-child(1)`)
        .snapshot('Shows popup'),
  ],