code: def create_loopback(file_path):
      '''
      Create a loopback device for a given backing file.
  
      :returns: str: Full path to new loopback device (eg, /dev/loop0)
      '''
      file_path = os.path.abspath(file_path)
      check_call(['losetup', '--find', file_path])
      for d, f in six.iteritems(loopback_devices()):
          if f == file_path:
              return f create_loopback(file_path):
      '''
      Create a loopback device for a given backing file.
  
      :returns: str: Full path to new loopback device (eg, /dev/loop0)
      '''
      file_path = os.path.abspath(file_path)
      check_call(['losetup', '--find', file_path])
      for d, f in six.iteritems(loopback_devices()):
          if f == file_path:
              return d
docs: Create a loopback device for a given backing file.
  
      :returns: str: Full path to new loopback device (eg, /dev/loop0)