Incorporate comments

Author: Cheolsoo Park

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/ScalaUDF.scala

@@ -28,14 +28,12 @@ case class ScalaUDF(
     function: AnyRef,
     dataType: DataType,
     children: Seq[Expression],
-    expectedInputTypes: Seq[DataType] = Nil) extends Expression with ExpectsInputTypes {
+    inputTypes: Seq[DataType] = Nil) extends Expression with ExpectsInputTypes {
 
   override def nullable: Boolean = true
 
   override def toString: String = s"UDF(${children.mkString(",")})"
 
-  override def inputTypes: Seq[DataType] = expectedInputTypes
-
   // scalastyle:off
 
   /** This method has been generated by this script