How to use the d3-scale-chromatic.schemeDark2 function in d3-scale-chromatic

/**
 * Typescript definition tests for d3/d3-scale-chromatic module
 *
 * Note: These tests are intended to test the definitions only
 * in the sense of typing and call signature consistency. They
 * are not intended as functional tests.
 */

import * as d3ScaleChromatic from 'd3-scale-chromatic';

// -----------------------------------------------------------------------
// Categorical
// -----------------------------------------------------------------------
let accent: string = d3ScaleChromatic.schemeAccent[0]; // #7fc97f
let dark: string = d3ScaleChromatic.schemeDark2[0]; // #1b9e77
let paired: string = d3ScaleChromatic.schemePaired[0]; // #a6cee3
let pastel1: string = d3ScaleChromatic.schemePastel1[0]; // #fbb4ae
let pastel2: string = d3ScaleChromatic.schemePastel2[0]; // #b3e2cd
let set1: string = d3ScaleChromatic.schemeSet1[0]; // #e41a1c
let set2: string = d3ScaleChromatic.schemeSet2[0]; // #66c2a5
let set3: string = d3ScaleChromatic.schemeSet3[0]; // #8dd3c7

// -----------------------------------------------------------------------
// Diverging
// -----------------------------------------------------------------------
let BrBG: string = d3ScaleChromatic.interpolateBrBG(0); // rgb(84, 48, 5)
let PRGn: string = d3ScaleChromatic.interpolatePRGn(0); // rgb(64, 0, 75)
let PiYG: string = d3ScaleChromatic.interpolatePiYG(0); // rgb(142, 1, 82)
let PuOr: string = d3ScaleChromatic.interpolatePuOr(0); // rgb(127, 59, 8)
let RdBu: string = d3ScaleChromatic.interpolateRdBu(0); // rgb(103, 0, 31)
let RdGy: string = d3ScaleChromatic.interpolateRdGy(0); // rgb(103, 0, 31)

green_blue_white_diverging, red_blue_white_diverging,
  red_black_white_diverging
} from './symbolSchemes';
import * as _ from 'd3-scale-chromatic';
import {interpolateRgbBasis} from 'd3-interpolate';
import {peek} from 'vega-util';

var discretized = {
  blueorange:  blueOrange
};

var schemes = {
  // d3 categorical palettes
  category10:  _.schemeCategory10,
  accent:      _.schemeAccent,
  dark2:       _.schemeDark2,
  paired:      _.schemePaired,
  pastel1:     _.schemePastel1,
  pastel2:     _.schemePastel2,
  set1:        _.schemeSet1,
  set2:        _.schemeSet2,
  set3:        _.schemeSet3,

  // additional categorical palettes
  category20:  category20,
  category20b: category20b,
  category20c: category20c,
  tableau10:   tableau10,
  tableau20:   tableau20,

  // sequential multi-hue interpolators
  viridis:     _.interpolateViridis,

import TitleBar from './TitleBar'

import RawInteractionPanel from './RawInteractionPanel'
import GeneList from './GeneList'
import Immutable from 'immutable'
import FilterPanel from './FilterPanel'


import Loading from '../Loading'
import OpenIcon from '@material-ui/core/icons/action/open-in-new'

import * as d3Scale from 'd3-scale'
import * as d3ScaleChromatic from 'd3-scale-chromatic'

const colorFunction = d3Scale.scaleOrdinal(d3ScaleChromatic.schemeDark2)

const descriptionStyle = {
  background: '#BEBEB4',
  padding: '0.2em'
}

const disabledStyle = {
  background: '#999999'
}


class ClixoDetails extends Component {


  constructor(props) {
    super(props)