Adjusting line thickness (borderWidth) on line chart

Hello,

I would like to adjust the line width on a line chart. I tried the below theme

return array(
	 'colors' => array(
		 '#2559a7',
		 '#facd42',
                 '#199ED7',
		 '#bd8684',
		 '#3DA2AE',
		 '#de8c59',
	 ),
	 'points' => array(
		 array(
			 'point' => array(
				 // Circle
				 'pointStyle' => 'circle',
				 'pointRadius' => 0
			 ),
		 )
		),
		'elements' => array(
			array(
				'line' => array(
					'borderWidth' => 1
				),
			)
		),
 );

The color and point options work but not the borderWidth . What structure is needed for the theme so the options are picked up correctly? Chart.js doc on borderWidth.