scala> val array = Array("age","astro")
array: Array[String] = Array(age, astro)

scala> val baseRdd = sc.parallelize(array)
baseRdd: org.apache.spark.rdd.RDD[String] = ParallelCollectionRDD[0] at parallelize at <console>:29

scala> val flat2 = baseRdd2.flatMap(x => x.contains("a"))
<console>:31: error: type mismatch;
 found   : Boolean
 required: TraversableOnce[?]
         val flat2 = baseRdd2.flatMap(x => x.contains("a"))