change valid_prefix() to valid_path(): use label as another argument
change valid_prefix() to valid_path(): use label as another argument

fboehm/cboettig_site,fboehm/cboettig_site,fboehm/labnotebook,antass/labnotebook3,fboehm/labnotebook,fboehm/labnotebook,fboehm/cboettig_site,fboehm/cboettig_site,antass/labnotebook3,fboehm/cboettig_site,fboehm/labnotebook,fboehm/labnotebook,fboehm/labnotebook,antass/labnotebook3