func (b *BufferedSeriesIterator) PeekBack(n int) (t int64, v float64, ok bool) {
	return b.buf.nthLast(n)
}
func (b *BufferedSeriesIterator) PeekBack(n int) (t int64, v float64, ok bool) {
	return b.buf.nthLast(n)
}
func ( b * BufferedSeriesIterator ) PeekBack ( n int ) ( t int64 , v float64 , ok bool ) { return b . buf . nthLast ( n ) }
// PeekBack returns the nth previous element of the iterator. If there is none buffered,
// ok is false.
PeekBack returns the nth previous element of the iterator . If there is none buffered ok is false .