function convertBase(base) {
    var deconstructedValue = getValueAndUnit(base);
    if (deconstructedValue[1] === 'px') {
      return parseFloat(base);
    }
    if (deconstructedValue[1] === '%') {
      return parseFloat(base) / 100 * defaultFontSize;
    }
    throw new PolishedError(78, deconstructedValue[1]);
  }
Convert pixel value to rems. The default base value is 16px, but can be changed by passing a
second argument to the function.
@function
@param {string|number} pxval
@param {string|number} [base='16px']
@example
// Styles as object usage
const styles = {
  'height': rem('16px')
}

// styled-components usage
const div = styled.div`
  height: ${rem('16px')}
`

// CSS in JS Output

element {
  'height': '1rem'
}