@Override
    public int hashCode() {
        int result = getFrom();
        result = 31 * result + getTo();
        return result;
    }
Checks if the text covered by another span is within the text covered by this span.

@param o the other SpanNode to check.
@return true if the text covered by another span is within the text covered by this span, false otherwise.
document/src/main/java/com/yahoo/document/annotation/SpanNode.java