get_identifier

Get the identifier of this TimeZone, as passed to TimeZone.

If the identifier passed at construction time was not recognised, `UTC` will be returned. If it was null, the identifier of the local timezone at construction time will be returned.

The identifier will be returned in the same format as provided at construction time: if provided as a time offset, that will be returned by this function.

Parameters:

this	a TimeZone

Returns:

identifier for this timezone