For uploaded file in cms, where filename replace special characters with '_' in EDX Platform ?

[Lear]

Hi ,

when file is uploaded in a edx course in cms,  file metadata (including filename) is saved in fs.files collection at edxapp database.  filename here replace special characters with '_'.  Which edx code does this process in  EDX Platform (https://github.com/edx/edx-platform)

Thanks