How to use the britecharts/dist/umd/colors.min.colorGradients function in britecharts

this.line.on('customMouseOut', function () {
                    that.chartTooltip.hide();
                });
            }
            if (this.chartConfig.hasOwnProperty('colors')) {
                if (this.chartConfig['colors'].hasOwnProperty('colorSchema')) {
                    if (colors.colorSchemas.hasOwnProperty(this.chartConfig['colors']['colorSchema'])) {
                        this.line.colorSchema(colors.colorSchemas[this.chartConfig['colors']['colorSchema']]);
                    }
                }
                else if (this.chartConfig['colors'].hasOwnProperty('customSchema')) {
                    this.line.colorSchema(this.chartConfig['colors']['customSchema']);
                }
                if (this.chartConfig['colors'].hasOwnProperty('singleLineGradient')) {
                    if (colors.colorGradientsHuman.hasOwnProperty(this.chartConfig['colors']['singleLineGradient'])) {
                        this.line.lineGradient(colors.colorGradients[this.chartConfig['colors']['singleLineGradient']]);
                    }
                }
                else if (this.chartConfig['colors'].hasOwnProperty('customsingleLineGradient')) {
                    this.line.lineGradient(this.chartConfig['colors']['customsingleLineGradient']);
                }
            }
            lineContainer.datum(this.data).call(this.line);
            if (this.chartConfig.hasOwnProperty('click')) {
                this.line.on('customDataEntryClick', function (e, d, m) {
                    that.chartConfig['click'](e, d, m);
                });
            }
            if (showTooltip) {
                for (var option in this.chartConfig['tooltip']) {
                    if (this.chartTooltip.hasOwnProperty(option)) {
                        this.chartTooltip[option](this.chartConfig['tooltip'][option]);

that.chartTooltip.hide();
        });
      }

      if (this.chartConfig.hasOwnProperty('colors')) {
        if (this.chartConfig['colors'].hasOwnProperty('colorSchema')) {
          if (colors.colorSchemas.hasOwnProperty(this.chartConfig['colors']['colorSchema'])) {
            this.line.colorSchema(colors.colorSchemas[this.chartConfig['colors']['colorSchema']]);
          }
        } else if (this.chartConfig['colors'].hasOwnProperty('customSchema')) {
          this.line.colorSchema(this.chartConfig['colors']['customSchema']);
        }

        if (this.chartConfig['colors'].hasOwnProperty('singleLineGradient')) {
          if (colors.colorGradientsHuman.hasOwnProperty(this.chartConfig['colors']['singleLineGradient'])) {
            this.line.lineGradient(colors.colorGradients[this.chartConfig['colors']['singleLineGradient']]);
          }
        } else if (this.chartConfig['colors'].hasOwnProperty('customsingleLineGradient')) {
          this.line.lineGradient(this.chartConfig['colors']['customsingleLineGradient']);
        }
      }

      lineContainer.datum(this.data).call(this.line);

      if (this.chartConfig.hasOwnProperty('click')) {
        this.line.on('customDataEntryClick', function (e, d, m) {
          that.chartConfig['click'](e, d, m);
        });
      }

      if (showTooltip) {
        for (let option in this.chartConfig['tooltip']) {