Why didn't you just pass one element list with your class with it, for example:

  class MyClass:
     pass

  class_list = [MyClass]
  third_party_function(class_list)
  # or just 
  third_party_function([MyClass])

?

creating some simple wrapper for third party function, e.g.

  def wrapper(C):
     third_party_function([C])

could also be much simpler solution :)

But it's maybe off topic.