minor: remove default

[jkao97]

Change Description

Change to semaphore allows to not needing to specify default value for required parameters.

Testing

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[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}