code: func (muf *MutableForest) Delete(prefix []byte) (*CommitID, error) {
  	bs, removed := muf.commitsTree.Delete(prefix)
  	if !removed {
  		return nil, nil
  	}
  	return UnmarshalCommitID(bs)
  }
docs: // Delete a tree - if the tree exists will return the CommitID of the latest saved version