InfluxDb flux query: filter by time

Question

I have this flux aggregation query

from(bucket: db)
|> range(start: dateFrom, stop: dateTo)
|> filter(fn: (r) => r._measurement == tableName and (r._field == "value"))
|> filter(fn: (r) => (r.sensorId == "sensor1") 
                    or (r.sensorId == "sensor2") 
                    or (r.sensorId == "filter_sensor"))
|> aggregateWindow(every: 30s, fn: mean)
|> keep(columns: ["_time", "sensorId", "_value"])
|> pivot(rowKey:["_time"], columnKey: ["sensorId"], valueColumn: "_value")
|> yield(name:"result")

I need to remove before aggregation rows for all tags with _time when "filter_sensor" == 1 (when filter_sensor equals 1 - so it is invalid data and this time must be ignored in the aggregation) How I can do this? Thanks for reading and responses.