Insert data into external mateview with using data in internal mateview cache

Issue

There is an external mateview which is based on internal mateview.
This query explained in the official document[1] does not the use cache in internal mateview.

insert into target_table select * from matview option nocache

How to use the cache in the internal mateview?

[1]
https://access.redhat.com/documentation/en-US/Red_Hat_JBoss_Data_Virtualization/6.2/html/Development_Guide_Volume_5_Caching_Guide/sect-External_Materialization.html#External_Materialization_Usage_Steps