private void calculateTo() {
        int greatestTo = Integer.MIN_VALUE;
        for (SpanNode n : children()) {
            greatestTo = Math.max(n.getTo(), greatestTo);
        }
        cachedTo = greatestTo;
    }
Returns the character index where this {@link SpanNode} starts (inclusive), i.e.&nbsp;the smallest {@link com.yahoo.document.annotation.SpanNode#getFrom()} of all children.

@return the lowest getFrom() of all children, or -1 if this SpanList has no children.
document/src/main/java/com/yahoo/document/annotation/SpanList.java