    toolsView.focusTool(tool)

Focus the specified `tool` (of the `joint.dia.ToolView` type) within this tools view.

When a tool is focused, all other tools within this tools view are hidden and the tool's opacity is changed according to the tool's `focusOpacity` option. Only one tool can be focused at a time; the focus passes to the last tool within this tools view with which the `focusTool` function was called.

The effect of this function can be reversed by the `toolsView.blurTool` function.