[Ndn-interest] how to set freshnessSecond?

[ndn ndn]

Hello everyone,
I'm using NDN-CCL to writing a NDN application. But I find a problem about
data cache.
In NDN network ,all data can store in CS.But in my application,some content
always changing in 5 seconds,so I think setting a freshnessSecond will help
me solve this problem.
I try to setMustBefresh value,but it not works.The app also receive the
cached value.
But in NDN-CCL,I didn't find any method to set this?how to set it?

hope you give me some reply.

thanks.
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