set _tabIndex(val) {
      this.getTabInStripDomRef().setAttribute("tabindex", val);
    }
@class
The <code>ui5-tab</code> represents a selectable item inside a <code>ui5-tabcontainer</code>.
It defines both the item in the tab strip (top part of the <code>ui5-tabcontainer</code>) and the
content that is presented to the user once the tab is selected.

@abstract
@constructor
@author SAP SE
@alias sap.ui.webc.main.Tab
@extends sap.ui.webc.base.UI5Element
@tagname ui5-tab
@implements sap.ui.webc.main.ITab
@public