Converting type of a field in Elasticsearch Slow Logs scraped by filebeat

Hi team,

I am trying to plot some graphs using metrics scraped by filebeat from elasticsearch slow log files on kibana. But by default as the metric "elasticsearch.slowlog.took" is being created as keyword by filebeat , I am not able use it effectively. I tried changing it in the fields.yml file of filebeat which didn't work. So is there any way to change this or can we use convert processor of filebeat to achieve this?

Thanks