@Override
    public boolean equals(Object o) {
        if ( ! (o instanceof EmbedExpression other)) return false;
        if ( ! other.embedder.equals(this.embedder)) return false;
        return true;
    }
@return the requested embedder id. This will diverge from the selected embedder's id when executed in config-model
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/EmbedExpression.java