GROK filter throws ERROR

Elastic Stack Logstash
5

As you have suggest in Multiline issue with 2 different patterns for a single event I have put :

beats {
	port=>5044
	multiline {
	  pattern => "^%{TIMESTAMP_ISO8601}"
	  negate => true
	  what => "previous"
	}
}

and in the beginning of filter before anything I have put :

overwrite => ["message"]

should this configuration work for parsing.