code: func (b *PackedLongValuesBuilderImpl) Build() PackedLongValues {
  	b.finish()
  	b.pending = nil
  	values := make([]PackedIntsReader, b.valuesOff)
  	copy(values, b.values[:b.valuesOff])
  	ramBytesUsed := util.ShallowSizeOfInstance(reflect.TypeOf(&PackedLongValuesImpl{})) +
  		util.SizeOf(values)
  	return newPackedLongValues(b.pageShift, b.pageMask, values, b.size, ramBytesUsed)
  }
docs: /*
  Build a PackedLongValues instance that contains values that have been
  added to this builder. This operation is destructive.
  */