Production dependency on mypy_extensions via typing-inspect seems excessive

[stevecj]

In trying to see my my project depends on mypy_extensions in production, I found that it is due to dataclasses-json having a dependency on typing-inspect. From what I can see, typing-inspect is only used in 2 modules and only for its is_union_type function which is used once in each of those same modules.

Is there some other way to accomplish what that is being used for that would not require a dependency on typing-inspect?