The actual type would be a rather large union type, which would be unwieldy to use (but in an untyped system like python you still would need to deal with all of those corner cases to have a program that is correct in the face of arbitrary input).
Really the biggest annoyance of type systems is that they make you deal with corner cases that you don't think are practically possible. If you are right, then they are wasting your time. If you are wrong, then they are saving you from having bugs.
Dynamic languages really can have functions whose behavior cannot be expressed as some sort of type signature.
readAny :: forall c r. [TypeWithReadAnd c] -> String -> (forall a. c a => a -> r) -> Maybe r
readAny types string handle
Here's an example that uses Read as the serialization format and only deals with Int, Char and String; but hopefully you can imagine that I could replace the use of read with a per-type function that deserializes from a byte string or whatever.
read :: String -> Maybe Json
goes a long way.
You might want to return an error message on failure, or provide a mechanism for recovery, but those are somewhat specific to the use case and don't really address the key point of the article.
My point is that Python objects are certain data structure and if you bother to create type for it them then you can use it in function type.