How to use the vega-scale.isContinuous function in vega-scale

function includePad(type) {
  return isContinuous(type) && type !== Sequential;
}

function isContinuousColor(_) {
  const t = _.type;
  return isContinuous(t) && t !== Time && t !== UTC && (
    _.scheme || _.range && _.range.length && _.range.every(isString)
  );
}

function legendType(spec, scaleType) {
  var type = spec.type || Symbols;

  if (!spec.type && scaleCount(spec) === 1 && (spec.fill || spec.stroke)) {
    type = isContinuous(scaleType) ? Gradient
      : isDiscretizing(scaleType) ? Discrete
      : Symbols;
  }

  return type !== Gradient ? type
    : isDiscretizing(scaleType) ? Discrete
    : Gradient;
}