code: function ()
  	{
  		var
  			nButton,
  			columns = this.s.dt.aoColumns;
  
  		if ( $.inArray( 'all', this.s.aiExclude ) === -1 ) {
  			for ( var i=0, iLen=columns.length ; i<iLen ; i++ )
  			{
  				if ( $.inArray( i, this.s.aiExclude ) === -1 )
  				{
  					nButton = this._fnDomColumnButton( i );
  					nButton.__columnIdx = i;
  					this.dom.buttons.push( nButton );
  				}
  			}
  		}
  
  		if ( this.s.order === 'alpha' ) {
  			this.dom.buttons.sort( function ( a, b ) {
  				var titleA = columns[ a.__columnIdx ].sTitle;
  				var titleB = columns[ b.__columnIdx ].sTitle;
  
  				return titleA === titleB ?
  					0 :
  					titleA < titleB ?
  						-1 :
  						1;
  			} );
  		}
  
  		if ( this.s.restore )
  		{
  			nButton = this._fnDomRestoreButton();
  			nButton.className += " ColVis_Restore";
  			this.dom.buttons.push( nButton );
  		}
  
  		if ( this.s.showAll )
  		{
  			nButton = this._fnDomShowXButton( this.s.showAll, true );
  			nButton.className += " ColVis_ShowAll";
  			this.dom.buttons.push( nButton );
  		}
  
  		if ( this.s.showNone )
  		{
  			nButton = this._fnDomShowXButton( this.s.showNone, false );
  			nButton.className += " ColVis_ShowNone";
  			this.dom.buttons.push( nButton );
  		}
  
  		$(this.dom.collection).append( this.dom.buttons );
  	}
docs: Loop through the columns in the table and as a new button for each one.
  @method  _fnAddButtons
  @returns void
  @private