code: func (m *idManager) remove(i uint64) *queue.TxBuffer {
  	if i >= uint64(len(m.ids)) {
  		return nil
  	}
  
  	desc := &m.ids[i]
  	b := desc.buf
  	if b == nil {
  		// The provided id is not currently assigned.
  		return nil
  	}
  
  	desc.buf = nil
  	desc.nextFree = m.freeList
  	m.freeList = i
  
  	return b
  }
docs: // remove retrieves the tx buffer associated with the given ID, and removes the
  // ID from the assigned table so that it can be reused in the future.