docs: def docker2singularity(self, runscript="/bin/bash", force=False):
      '''docker2singularity will return a Singularity build recipe based on
         a the loaded recipe object. It doesn't take any arguments as the
         recipe object contains the sections, and the calling function 
         determines saving / output logic.
      '''
  
      recipe = ['Bootstrap: docker']
      recipe += [ "From: %s" %self.fromHeader ]
    
      # Sections with key value pairs
      recipe += self._create_section('files')
      recipe += self._create_section('labels')
      recipe += self._create_section('install', 'post')
      recipe += self._create_section('environ', 'environment')    
  
      # Take preference for user, entrypoint, command, then default
      runscript = self._create_runscript(runscript, force)
      recipe += finish_section(runscript, 'runscript')
  
      if self.test is not None:
          recipe += finish_section(self.test, 'test')
  
      # Clean up extra white spaces
      return '\n'.join(recipe).replace('\n\n','\n')