isinstance() takes a tuple of classes for the second argument. It’ll return true if the first argument is an instance of any of the types in that sequence:
isinstance(var, (classinfo1, classinfo2, classinfo3))
In other words, isinstance() already offers this functionality, out of the box.
From the isinstance() documentation:
If classinfo is neither a class object nor a type object, it may be a tuple of class or type objects, or may recursively contain other such tuples (other sequence types are not accepted).
Emphasis mine; note the recursive nature; (classinfo1, (classinfo2, classinfo3)) is also a valid option.