new_contents: 
  import os
  import platform
  
  def provide_system_boot_type():
  
      if platform.system() == 'Linux':
          # See also:
          #  http://askubuntu.com/a/162896
          if os.path.exists('/sys/firmware/efi'):
              return { 'system_boot_type': 'UEFI' }
          else:
              return { 'system_boot_type': 'BIOS' }
      else: 
          return { 'system_boot_type': False }
  
  
subject: Implement custom grain: system_boot_type