code: @Override
  	public void setChildren(Tree[] children) {
  		if (children == null) {
  			daughterTrees = EMPTY_TREE_ARRAY;
  		} else {
  			daughterTrees = children;
  		}
  	}
docs: Sets the children of this <code>Tree</code>.  If given
  <code>null</code>, this method prints a warning and sets the
  Tree's children to the canonical zero-length Tree[] array.
  Constructing a LabeledScoredTreeLeaf is preferable in this
  case.
  
  @param children An array of child trees