How to use the @carbon/icons/lib/chevron--down/20 function in @carbon/icons

_handleSlotChangeTitleIcon: handleSlotChangeTitleIcon,
    } = this;
    return html`
      <button class="${prefix}--side-nav__submenu" aria-expanded="${String(Boolean(expanded &amp;&amp; !forceCollapsed))}" aria-haspopup="true" type="button">
        <div class="${prefix}--side-nav__icon" hidden="" id="title-icon-container">
          
        </div>
        <span class="${prefix}--side-nav__submenu-title">${title}</span>
        <div class="${prefix}--side-nav__icon ${prefix}--side-nav__icon--small ${prefix}--side-nav__submenu-chevron">
          ${ChevronDown20()}
        </div>
      </button>
      <ul role="menu" class="${prefix}--side-nav__menu">
        
      </ul>
    `;
  }