docs: def apply(key, value):
      '''
      Set a single key
  
      .. note::
  
          This will strip comments from your config file
      '''
      path = __opts__['conf_file']
      if os.path.isdir(path):
          path = os.path.join(path, 'master')
      data = values()
      data[key] = value
      with salt.utils.files.fopen(path, 'w+') as fp_:
          salt.utils.yaml.safe_dump(data, default_flow_style=False)