Fixed lint errors

Signed-off-by: Joshua Au <[email protected]>

src/main/kotlin/org/opensearch/indexmanagement/indexstatemanagement/model/ExplainFilter.kt

@@ -25,8 +25,7 @@ data class ExplainFilter(
     val state: String? = null,
     val actionType: String? = null,
     val failed: Boolean? = null
-) : Writeable {
-
+) : ToXContentObject, Writeable {
 
     @Throws(IOException::class)
     constructor(sin: StreamInput) : this(
@@ -36,6 +35,19 @@ data class ExplainFilter(
         failed = sin.readOptionalBoolean()
     )
 
+    override fun toXContent(builder: XContentBuilder, params: ToXContent.Params): XContentBuilder {
+        builder.startObject()
+        builder.startObject(FILTER_FIELD)
+
+        if (policyID != null) builder.field(POLICY_ID_FIELD, policyID)
+        if (state != null) builder.field(STATE_FIELD, state)
+        if (actionType != null) builder.field(ACTION_FIELD, actionType)
+        if (failed != null) builder.field(FAILED_FIELD, failed)
+
+        builder.endObject()
+        return builder.endObject()
+    }
+
     @Throws(IOException::class)
     override fun writeTo(out: StreamOutput) {
         out.writeOptionalString(policyID)