Overloaded getter/setter in ES6 class produces wrong output

The [recipes doc](https://github.com/documentationjs/documentation/blob/master/docs/RECIPES.md#overloaded-methods) illustrates how to document a method that is an overloaded getter/setter depending on parameters. But the following code produces what I believe to be wrong output:

```
class RTLSDR extends EventEmitter {
// ...

/**
* Get the device's crystal frequencies.
* @return {XtalFreqs} - current crystal frequencies
* @throws {Error} the device is closed
*/
/**
* Set the device's crystal frequency(ies).
* @param {number} rtlFreq - the crystal frequency to set on the RTL device
* @param {number} [tunerFreq=rtlFreq] - the crystal frequency to set on the tuner, if different
* @return {this}
* @throws {Error} the device is closed
*/
xtalFreq(rtlFreq, tunerFreq) {
this.assertOpen();

if (rtlFreq) {
librtlsdr.set_xtal_freq(this.device, rtlFreq, tunerFreq || rtlFreq);
return this;
}

return librtlsdr.get_xtal_freq(this.device);
}

// ...
} // end of class
```

This produces two signatures in the HTML output (which is correct) but the "get" signature is not what I want:

> Get the device's crystal frequency(ies).
> xtalFreq(rtlFreq: any, tunerFreq: any): XtalFreqs
>
> Set the device's crystal frequency(ies).
> xtalFreq(rtlFreq: number, tunerFreq: [number]): this

I believe the "get" output should be:

> Get the device's crystal frequency(ies).
> xtalFreq(): XtalFreqs