COMPAT: Don't use re module's private type

[TomAugspurger]

pandas/pandas/core/dtypes/inference.py

Line 219 in c4b4a81

return isinstance(obj, re._pattern_type)

In 3.6+ there's typing.re.Pattern. Otherwise, there's _re_type = type(re.compile('')).

[jreback]

is there a pep reference for this?

[TomAugspurger]

I assume not, since it's a private attribute.