code: func (rt *skipListRT) InsertAtDimension(dimension uint64,
  	index, number int64) (rangetree.Entries, rangetree.Entries) {
  
  	if dimension >= rt.dimensions || number == 0 {
  		return rangetree.Entries{}, rangetree.Entries{}
  	}
  
  	affected := make(rangetree.Entries, 0, 100)
  	var deleted rangetree.Entries
  	if number < 0 {
  		deleted = make(rangetree.Entries, 0, 100)
  	}
  
  	rt.insert(rt.top, 0, dimension, index, number, &deleted, &affected)
  	rt.number -= uint64(len(deleted))
  	return affected, deleted
  }
docs: // InsertAtDimension will increment items at and above the given index
  // by the number provided.  Provide a negative number to to decrement.
  // Returned are two lists.  The first list is a list of entries that
  // were moved.  The second is a list entries that were deleted.  These
  // lists are exclusive.