Update pqmf.py to fix import error

[sunnyghost2016]

PR types

Bug fixes

PR changes

Others

Describe

update pqmf.py to fix import error

[CLAassistant]

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.}

[lakako]

Already fix this in #3736

[zxcd]

Thanks for your contribution, this problem already been fix in #3818