units = [
    'em', 'ex', 'ch', 'rem',  # relative lengths
    'vw', 'vh', 'vmin', 'vmax',  # relative viewport-percentage lengths
    'cm', 'mm', 'in', 'pt', 'pc', 'px',  # absolute lengths
    'deg', 'grad', 'rad', 'turn',  # angles
    's', 'ms',  # times
    'Hz', 'kHz',  # frequencies
    'dpi', 'dpcm', 'dppx', 'x',  # resolutions
    '%',  # percentage type
    'fr'  # grid-layout (http: #www.w3.org/TR/css3-grid-layout/)
]
