public String getPrefix(int toNotIncluding) {
        if (toNotIncluding > 0) {
            return toString(0, toNotIncluding) + "/";
        }
        return "";
    }
<p>Returns the prefix of this hop's selector to, but not including, the
given index.</p>

@param toNotIncluding The index to which to generate prefix.
@return The prefix before the index.
messagebus/src/main/java/com/yahoo/messagebus/routing/Hop.java