add examples

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

@@ -37,6 +37,10 @@ import org.apache.spark.util.Utils
   usage = """
     _FUNC_(child, jsonFormatSchema, options) - Converts a binary Avro value into a Catalyst value.
     """,
+  examples = """
+    > SELECT IS_NULL(_FUNC_(result, '{"type": "record", "name": "struct", "fields": [{ "name": "u", "type": ["int","string"] }]}')) AS result FROM (SELECT NAMED_STRUCT('u', NAMED_STRUCT('member0', member0, 'member1', member1)) AS s FROM VALUES (1, NULL), (NULL,  'a') tab(member0, member1));
+     [false]
+  """,
   note = """
     The specified schema must match actual schema of the read data, otherwise the behavior
     is undefined: it may fail or return arbitrary result.
@@ -121,6 +125,10 @@ case class FromAvroSqlFunction(child: Expression, jsonFormatSchema: Expression,
     _FUNC_(child, jsonFormatSchema) - Converts a Catalyst binary input value into its corresponding
       Avro format result.
   """,
+  examples = """
+    > SELECT IS_NULL(_FUNC_(result, '{"type": "record", "name": "struct", "fields": [{ "name": "u", "type": ["int","string"] }]}', MAP() ).u FROM (SELECT FROM_AVRO(result, '{"type": "record", "name": "struct", "fields": [{ "name": "u", "type": ["int","string"] }]}' ) AS result FROM (SELECT NAMED_STRUCT('u', NAMED_STRUCT('member0', member0, 'member1', member1)) AS s FROM VALUES (1, NULL), (NULL,  'a') tab(member0, member1)));
+     [false]
+  """,
   group = "misc_funcs",
   since = "4.0.0"
 )