code: func (b *PackedLongValuesBuilderImpl) Add(l int64) PackedLongValuesBuilder {
  	assert2(b.pending != nil, "Cannot be reused after build()")
  	if b.pendingOff == len(b.pending) { // check size
  		if b.valuesOff == len(b.values) {
  			newLength := util.Oversize(b.valuesOff+1, 8)
  			b.grow(newLength)
  		}
  		b.pack()
  	}
  	b.pending[b.pendingOff] = l
  	b.pendingOff++
  	b.size++
  	return b
  }
docs: /* Add a new element to this builder. */