Moves to the next data element in the current segment.
The 'callback' parameter specifies a function which will be called when the operation completes (or an error is encountered). If the 'callback' parameter is not specified, then the method will block and will not return until the operation completes (or an error is encountered).
The callback for this method is defined as:
'err' is the error that occurred. If there was no error, then 'err' is 'null'.
'err' has 2 properties which hold detailed information:
SkipElement can be used to avoid providing a value for the current element in the current segment.
If the element already has a value (such as one provided by default by the class), said value will not be overwritten.