Column Chart - xaxis categories and labels formatter strange behaviour

[Flertz]

Hi. After updating to the latest version, it seams to me that the xaxis categories and labels formatter has a strange behaviour. According to code, labels formatter could return both a string or an array of strings.

formatter?(value: string, timestamp?: number, opts?:any): string | string[]

In the older versions each element of the array was rendered as a row (same result with categories). But now, with the latest version, each row contains the whole array.

xaxis: {
             labels: {
                                rotate: 0,
                                formatter: (value: string, timestamp: number, opts: object) => {
                                    return ['foo', 'bar']
                                }
                            },
                            axisTicks: { show: false }
                }