code: def _arg(self, line):
          '''singularity doesn't have support for ARG, so instead will issue
             a warning to the console for the user to export the variable
             with SINGULARITY prefixed at build.
   
             Parameters
             ==========
             line: the line from the recipe file to parse for ARG
     
          '''
          line = self._setup('ARG', line)
          bot.warning("ARG is not supported for Singularity! To get %s" %line[0])
          bot.warning("in the container, on host export SINGULARITY_%s" %line[0]f _arg(self, line):
          '''singularity doesn't have support for ARG, so instead will issue
             a warning to the console for the user to export the variable
             with SINGULARITY prefixed at build.
   
             Parameters
             ==========
             line: the line from the recipe file to parse for ARG
     
          '''
          line = self._setup('ARG', line)
          bot.warning("ARG is not supported for Singularity! To get %s" %line[0])
          bot.warning("in the container, on host export SINGULARITY_%s" %line[0])
docs: singularity doesn't have support for ARG, so instead will issue
             a warning to the console for the user to export the variable
             with SINGULARITY prefixed at build.
   
             Parameters
             ==========
             line: the line from the recipe file to parse for ARG