public int getLength(int i) {
        return getTo(i) - getFrom(i);
    }
Returns the length of this span according to subtree i, i.e.&nbsp;getFrom(i) - getTo(i).

@param i the index of the subtree to use
@return the length of this span according to subtree i
document/src/main/java/com/yahoo/document/annotation/AlternateSpanList.java